Tow vehicle engine oil

[W. M. Hellinger]

I'm changing the engine oil in my new-to-me (used) Tahoe. I'm fixin to drive approx. 3000 miles basically non-stop at interstate speeds, pulling approx. 2,500 lbs. of trailer. The Tahoe manual recommends 5-30wt. motor oil. This is the first vehicle I've owned that calls for 5-30wt. motor oil. I've been running Delo 400 15-40wt. in every rig I've owned for the past 20 years. I'm feeling kind-of uneasy about this 5-30wt. oil, especially in a vehicle that's going to be working hard at sustained high RPMs hour after hour.

 

Any thoughts?

 

Also, I've always filled my highway cruisers just a touch over full, approx. 1/4 pint over the recommended capacity... because I'm of the opinion that at sustained highway driving, a fair amount of oil is up in the motor. With this 5wt. oil, I expect it will drain back down into the pan faster.

 

Any thoughts?

[RoadRanger]

Mobil One 5w30 . Engines typically can run 2 quarts down before having "issues" - putting in too much oil can cause increased consumption and reduced MPG as the oil sloshes around more and interferes with the crank. I usually run between 1/2 and 1 quart low. Thicker oil pumps slower and can reduce lubrication - especially in cold weather. It also reduces fuel mileage. Modern oils have much higher film strengths than oils did 20 years ago .

[basschaplain]

Depending on the age and oil history of the Tahoe, you may consider not using Mobile 1.

Sometimes there can be a problem introducing synthetic oil to older vehicles.

True synthetic oil (Group IV & V) can clean the inside of the engine (and seals). If the vehicle has had dinosaur oil for several years, it is possible that the seals, once cleaned, could start leaking.

A lot of might/could/may/possible, but something to consider.

hydro cracked oils should be ok though.

Oh, and I had the same question about puting 5W-30 in my truck. I just put 5W-30 in it for the first time. But the warmest I'll be driving in till may is upper 20s and it'll be down in the -30 range come February. Oils and vehicles today aren't like what we started with way back ...

Both the Castrol and Mobil1 websites recommend 5W-30 for the Tahoe and also trucks that tow trailers.

[W. M. Hellinger]

 

Oils and vehicles today aren't like what we started with way back ... Both the Castrol and Mobil1 websites recommend 5W-30 for the Tahoe and also trucks that tow trailers.

 

 

I wonder how much of that "information" relates to someone who starts their vehicle and drives for a day on interstates, and how much of that information relates to someone who's doing 50mph (or 70mph) within a minute of starting their vehicle, just to shut it off after a 10 minute (or 2 hour) commute (depending on the traffic situation) ???

[glepko]

follow the advice in your manual. the only thing you should do under extreme use (this qualifies) is change the oil more frequently.

[W. M. Hellinger]

 

follow the advice in your manual.

 

Surely you're joking.

 

The factory supplied owners manual appears to be 7-12 + 14 pages of legalease... basically page after page of "consult your dealer".

 

They don't even seem to have enough confidence that they can get the paperwork right to stipulate the crankcase capacity of the engine, much-less anything else. I determined the proper re-fill quantity by weighing what came out.

 

Obviously they don't have enough faith in their "people" to include the correct manual with the vehicle, so they print a "hear no evil, see no evil, speak no evil" fits-all manual. Or maybe it's a case of "make no statement that might hold-up in court"?

 

And we all wonder what's wrong with GM? (I don't think b...b...b... BILLIONS is gonna solve anything).

[RoadRanger]

I determined the proper re-fill quantity by weighing what came out.

Didn't come with a dipstick ?

[W. M. Hellinger]

Didn't come with a dipstick ?

Yes.

 

And like most everything else on the vehicle, the calibrations on the dipstick are picturegraphs vaguely referring to "something" ... obviously they don't sell enough of these vehicles in the country which they are "made" to dedicate signage to the local language (possibly English?).

 

Besides, guessing how much to refill is fine if you guess low. If you guess high (as later determined by a dipstick sticking), changing the level (to involve less) generally makes a mess on the shop floor.

 

I have a platform scale that reads to the 0.01lb. So weighing what came out (with a full dipstick) seemed like the best determination of what should go in (after pooling through hundreds of pages in the owners manual and coming up empty handed).

 

A credit to this forum:

 

I've determined (after searching on-line for a straight forward answer to Tahoe engine crankcase capacities) that this forum is in the upper 1%... being: if you ask a straight forward question here, generally you'll get a straight forward answer here... as opposed to the other 99%+ of forums out there.

[Dogoth]

I can't imagin putting a little heavier oil in it, specificly for this long trip would hurt a thing (as a matter of fact it probably would be beneficial). It is true that newer designed vehicles (as a general rule) are made to run on thinner oil (smaller oil galleries, different pump etc...) but you're not going off the deep end running 20-50 wt either. I'm sure the oil spec is based on an average. Since you live in a slightly cooler climate than average (Washington state yes?). then lighter oil will provide lubrication quicker on those cold morning starts (The first 5 minutes of operation from cold is where probably 90% of the engine wear occurs) so yea when you're done with your trip, go back to the factory spec. I have an 04 Ford (same spec of oil weight). Once the warranty was up, I started running about 5 points heavier oil in the hot summer. Seems like common sense to me.

[RoadRanger]

Besides, guessing how much to refill is fine if you guess low. If you guess high (as later determined by a dipstick sticking), changing the level (to involve less) generally makes a mess on the shop floor.

I usually throw in 3 quarts, then:

1) wait a minute then check the stick. Throw in another if it doesn't indicate at all then repeat.

2) let it set for a while (10 minutes?) so all the oil drains into the crankcase and if it is below the "add" mark throw in another. Repeat.

3) run it five minutes, shut down for 10, then add oil to half way between the "full" and "add" marks which are usually 1 quart apart.

 

Then when checking it I add a half a quart if it gets down to the "add" mark.

 

BTW Mobile One and most (all?) consumer grade synthetic motor oils are made with a petroleum base oil that doesn't dry out seals like the full synthetics. A lot of these little "old wive's tales" are from the very first synthetics before Mobile One came out. I change my oil about every 30k or so .

[W. M. Hellinger]

 

I usually throw in 3 quarts, then: 1) wait a minute then check the stick. Throw in another if it doesn't indicate at all then repeat. 2) let it set for a while (10 minutes?) so all the oil drains into the crankcase and if it is below the "add" mark throw in another. Repeat. 3) run it five minutes, shut down for 10, then add oil to half way between the "full" and "add" marks which are usually 1 quart apart.

 

That's one way to do it.

 

That Tahoe proved to have an approx. 6 1/2 qt. crankcase capacity.

 

Weighing the oil that came out took approx. 5 seconds.

 

BTW: I don't trust dipsticks on new to me used vehicles. My new to me used astrovan registers full on the dipstick that came with the van at somewhere around 2 qts. (it has a 5 qt. system). I have since purchased a new dipstick for that van... from a chevy dealership... based on the VIN of the van. The new (factory correct) dipstick might register full at somewhere around 10qts. (just judging by the fact that 5qts. didn't even register.) I'm currently using the old dipstick, with some new marks on it.

[whataracket]

I have a 2004 GMC Yukon XL (Suburban) with the 5.3 liter engine. The manual says it takes six quarts to fill after draining the oil and installing a new filter, and the dipstick reads just a hair low after adding six quarts, running it for a while, and letting it settle. The manual says the 4.8 and 6.0 liter engines take the same amount. I have run Mobil 1 5W-30 since the end of break in.

 

The dealers' service departments have told me they recommend 5W-30 because "engines are built tighter today." However, one of my friends at work who is an expert on BMW mechanical design and service (he races as a hobby) is convinced that the manufacturers primarily recommend the lighter weight oil to achieve higher gas mileage, at the expense of higher wear rates due to film breakdown under high loads. Who knows? I have run the recommended oil weight for 70k miles in my Yukon and it burns about a half quart between 5000 mile oil changes. Pretty good.

 

Regarding towing, 2500 lbs. is not a heavy load for that truck to pull, and highway towing that weight shouldn't be that hard on it. I'd be more worried about your trailer bearings and tires on such a long drive. If it's a half ton Tahoe, it would be much better if you have trailer brakes. You're at or slightly above the safe trailer weight limit for towing without brakes. If you take it easy it will be OK for normal driving, but in a panic stop, particularly with a short wheelbase, you're are likely to jackknife if you skid. ABS helps, but it's not foolproof for this.

 

Assuming you bought a good one, I think you'll find it makes a great highway vehicle. The shorter wheelbase makes it a bit less stable than a Suburban at speed, but overall they drive really nice, especially if you install better shocks.

[Coaster]

i run 10-30 in my 318 (bored .30 over at about 180,000 miles)

 

with 65k on yours i'd say 10-30 would be fine.

[Dogoth]

Thoughts about synthetics.

 

There has been a light synthetic oil made for years called "Marvel Mystery oil". It is sold as a penetrating oil and it does wonders for freeing up badly rusted parts and wicking it's way into things. I have found that synthetic oil made for cars has some of the same properties. It lubricates VERY well for it's weight (I think this property is called viscosity - I'm not a chemist though so don't quote me on that one) and doesn't break down with heat as fast as plain old refined crude. It does however find any seal that has the potential to leak and make it do just that. It tends to act like penetrating oil so if everything is nice and tight and all of the gaskets are nice and fresh there is no problem but it has been my experience that if there is any possibility of a leak, synthetic oil will find it. That's just my belief and observations.

 

FWIW Even though it causes a few small seep leaks I still run it in my motorcycle because I think it withstands the heat of an air cooled high reving motor much better. I would LOVE to teflon treat my bike but (since it's shared crank & transmission oil) I don't think the wet clutch would work right after that :>).

 

Have a nice safe trip.

[jgthatsme]

I bought a Chevrolet Blazer (the big Blazer) new in June, 1993 and ran Mobil 1 5-30 grade through it until selling it last year w/ just over 297,000 miles on the engine. The engine never needed any work (other than a few plug & wire changes). That made me a believer in Mobil 1. I also never had any issues w/ the transmission. I dropped the pan once at around 200,000 miles and changed the filter. I believe twice before changing the filter and once after changing the filter I had one of those oil change places do a complete fluid change where they suck the old fluid out of one end while pumping fresh fluid in the other.

[popgadget]

The prime reason for the 5w30 call out in newer vehicles is CAFE (Corporate Average Fuel Efficiency). In simplistic terms, it means that the thinner oil has less friction and slightly increases mileage. The better the average fleet mileage, the more gas guzzlers they can build.

 

So the choice of oil spec has nothing to do with the lubricating quality of the oil.

Essentially there are two considerations to be concerned about, cold flow and film strength.

The lower the first number, the better the cold flow, the higher it is, the better the film strength. These two qualities are at odds with one another. You want good cold flow for startup, and high film strength for high temperature operation.

 

The only real advantage of a synthetic is that it can have very good cold flow with a high film strength for high temps as well. Any claims of extended change intervals are ludicrous. engine oil is polluted long before it is worn out. It is more important to get rid of the contaminants than any other oil related maintenance. Its far better to use "cheap oil" and change it often than to use the high buck synthetic and let it fill up with acids and sludge. Of course, if you have deep pockets, use Synthetic and change it often, there is no harm in using it, except in Powerstroke Diesels.

 

My suggestion would be to use 10-40 and a block heater to provide better flow for cold starts. Change it and the filter every 3,000 miles. Use an API SM rated oil, at that interval, the brand makes little difference. (If it is a Diesel, use CI-4). "S" ratings are for spark ignition engines, "C" ratings are for compression ignition engines.

[RoadRanger]

Weighing the oil that came out took approx. 5 seconds.

... but doesn't allow sufficient time for beer breaks . BTW how did you compensate for the oil left in the filter? Did you just dump the filter in the pan too then subtract the weight of a "new" filter"? Or did you just not count the oil used to prefill the filter?

[doug_h]

If you really want the lowdown on motor oils:

 

http://www.bobistheoilguy.com/forums/ubbthreads.php

 

 

a 5w-30 oil will be perfectly fine for your vehicle. Just keep an eye out for any consumption. Unless you are driving in sustained high temps a thicker oil won't prevent any more wear. Even newer motors that recommend 5w-20 are not blowing up all over the place. As long as it has been maintained well that tahoe should last you hundreds of thousands of miles.

[W. M. Hellinger]

... but doesn't allow sufficient time for beer breaks . BTW how did you compensate for the oil left in the filter? Did you just dump the filter in the pan too then subtract the weight of a "new" filter"? Or did you just not count the oil used to prefill the filter?

I always prefill the filter, if the filter hangs down, as it does on the Tahoe. Some folks think prefilling the filter is an exercise in futility, but... what the hey... it can't hurt.

 

I wasn't too concerned about getting a real accurate weight/measurement... just confirm what I'd read on-line concerning the crank case capacity of this vehicle... since it didn't seem to be specified anywhere in the owner's manual. What I found on-line seemed to suggest a capacity of 6 qts with the standard filter (which is a dinky small filter). I bought a bigger filter (taller), which I figured would take roughly an additional 1/3 qt. But I really wanted to confirm the 6qt. capacity of the oil-pan since my Tahoe is a special service model, and there seems to be differences between the special service model and the regular civilian model... and the specs I found on-line didn't specify the special service model.

[agedhorse]

The primary move towards lower viscosities is to improve fuel efficiencies. Not so much due to friction as due to the viscosity and sheering within the film, profile.

 

Using the same viscosity and type of lubericant, the film strength will generally be higher on higher viscosity oils. Under highter temps, a higher viscosity on the high temp side is no problem either.

 

Low viscosity oils may have better cold start capabilities, but for the type of driving Mark's going to be doing I would say there is no drawback to higher cold viscosity oils. I use 100% synthetics in my tow vehicles with no problems.

[W. M. Hellinger]

 

The primary move towards lower viscosities is to improve fuel efficiencies. Not so much due to friction as due to the viscosity and sheering within the film, profile. Using the same viscosity and type of lubericant, the film strength will generally be higher on higher viscosity oils. Under highter temps, a higher viscosity on the high temp side is no problem either. Low viscosity oils may have better cold start capabilities, but for the type of driving Mark's going to be doing I would say there is no drawback to higher cold viscosity oils. I use 100% synthetics in my tow vehicles with no problems.

 

It might be an old husband's tale, but years ago I read that 10-40wt. oil is basically 10wt. oil with additives to make it behave like 40wt. oil when it's hot. And: the additives break down (wear-out) with usage in the engine... to where eventually that 10-40wt. oil can basically revert to being just 10wt. oil. Where-as straight 30wt. oil is 30wt. when it goes in, and is 30wt. when it comes out.

 

This is part of what's got me a little squeemish about this recommended 5-30wt. oil. Is it gonna be basically 5wt. oil in a few thousand miles?

[boomerweps]

I'd use the 5W-30 that's recommended. How often do you change the oil? I change mine 2-3 times a year but I have 4 vehicles we use and my wife and I are officially retired so it's more a time vs. milage changing period.

 

3/4 are Fords and Ford came out with TSB on 01/21/02 that changed from the manual's 5w-30 to 5w-20 for the bulk of their vehicles. So I started using 5W-20 in my 98 Contour and Expedition. So far so good. Currently the 5.3L Expedition is my heavy load/tow vehicle & wife's winter 4x4. For the 4.0L Explorer, 5w-20 is NOT recommended, it stays with 5w-30.

 

While CAFE is a significant reason to switch to lighter weight oils, part of the recommendations is based on tighter tolerences inside engines. Since the vehicle was under a GM maintenance contract, it's likely worn in using the 5w-30 and I would NOT change to a heavier base weight oil now. I THINK there is a 5w-40 now, consider that for the summer oil change.

 

Boomerweps

[SpaceNorman]

I'm big on following the manufacturer's recommendations. I've got zero expertise in the area - and therefore no foundation on which to base a decision to use something else.

 

...and that's regardless of whatever disclaimers the little print has to say.

[Craig Vecchione]

As a former dealer wrench, I'll make the following recommendations:

 

Stop worrying. Today's engine oils are so much better than what was sold even 20 years ago it isn't even funny. 5w-30 will be fine. If there's a hard-service recommendation, use that, but otherwise go with what's specified.

 

Unless you run the same oil for 10's of thousands of miles you'll never have a problem with viscosity issues.

 

I heartily recommend Mobil-1. It was the first, and is still the best oil available. Well worth the price.

[popgadget]

 

It might be an old husband's tale, but years ago I read that 10-40wt. oil is basically 10wt. oil with additives to make it behave like 40wt. oil when it's hot. And: the additives break down (wear-out) with usage in the engine... to where eventually that 10-40wt. oil can basically revert to being just 10wt. oil. lesWhere-as straight 30wt. oil is 30wt. when it goes in, and is 30wt. when it comes out.

 

 

Actually a multiviscosity oil changes viscosity LESS than a straight weight oil. It provides the cold flow of the lower number and the film strength of the higher number. As it heats up it does not change viscosity anywhere near as much as a straight weight oil. At high temps it is just as "thick" as the straight weight.

This is accomplished by using a better base stock and/or adding VI (viscosity improver). VI is the additive that Mark is worried about wearing out. It is actually comprised of long chain polymers that act like bearings and provide the film strength. (Think STP) As the oil is used these chains get sheared in smaller bits until they no longer provide the film strength that they once did.

 

There is no chance of "wearing out" the additives in any acceptable change interval. As I said before the oil suffers from serious pollution long before it is worn out. This contamination is quite detrimental to the life of the engine, and is the most important reason to change your oil. It is also the basis for calendar time intervals for under utilized vehicles.

 

If you change you oil and filter every 3k, any API rated oil would be fine. If you want the best possible protection from extreme pressure wear, use an oil with a higher upper rating. Keep in mind, that your mileage may suffer slightly, and that you might add some wear on cold starts if the lower number went up as well.