looking at an 05 Tahoe 5.3 that was a municipal vehicle. Guy printed me off a copy of the records and it looks like they used Chevron URSA 15w40 every oil change since new. The engine sounded ok but I couldnt drive it. Normally I would expect to get at least another 100k out of a 5.3 with only 125k on it, but Im wondering if that oil would have helped it or hurt it for the long run?
15w40 for 125k good or bad?
- Thread starter slowride
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Some of the decision, IMO, would depend on where the vehicle is at and the weather. I believe the manual calls for 5W-30 and I run 10W-30 in my 2002 with 160k miles on it. I personally would not have ran 15W-40 in it and I, if I bought it, would run 10W-30 but it is up to you. Others will chime in.
HiHoeSilver
Away!
I agree that the climate plays a role here. 15w40 is pretty thick if you're somewhere that has a real winter.
SnowDrifter
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I run a thick 0w30 or a thin 0w40 in my rig depending on what sales are going on. I'm of the seemingly unpopular opinion that Anything other than 0wXX at this point in chemical development is outdated. Running 5/10/15wXX is just... Nonsensical? Second number is viscosity at operating temp. First number is how much it thickens when it gets cold / how little it thins out when it gets hot. I favor the flattest viscosity curve I can get. A 0wXX (i.e. something with a higher viscosity index) will both not thicken as much when it gets cold, and resist thinning out above 100c. Meh.
I also think there's a misconception about oil pressure and too much emphasis on it. Barring extremes, flow tends to be a more important metric than pressure, as pressure can be manipulated viscosity. Sure you can run a 10w60, peg your pressure gauge, and claim pressure is good. But pressure is just a resistance to flow. If you put a thicker fluid in there, certainly it will resist flow more and give an increase in pressure. But, and here's the big "but" I think is missed; Your oil pump has a pressure bypass valve. Stray too thick, that valve opens, and despite higher/"better" pressure, your oil flow rates through the engine are cut down.
Now, with all this said, there's a Goldilocks zone as far as appropriate oil viscosity to run. Too thin, and it'll run through all the holes inside the engine too quickly. Bearing tolerances, bearing width, oil hole flow diameter, lifter bleed off rates, oil control ring design, and oil pump flow need to be calibrated to a given viscosity. There needs to be enough resistance to flow so that oil can make the appropriate loop through the engine. (If this bit isn't clear let me know, I'll expand on it). Likewise, too thick and you won't get enough flow to replenish things like bearings and piston wall coverage between rotations.
Being that temperature plays such a large role in viscosity, whether 15w40 is appropriate really depends on your climate and drive style. If you're somewhere hot and working your rig hard towing or doing something else that would raise oil temperature (and lower viscosity), then yes it's probably appropriate. If not, then I might give it a second glance.
For better or for worse, you'll need to run your OCI out and get some analysis done on it to figure out what's appropriate for you. This fellow here played with some 0w20 and 0w40 in his rig and found that the 0w20 posted better wear numbers than the 40 weight did. https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/4382069/Thin_or_thick_(TGMO_0W-20/M1_0
Now that's a different engine and the conclusions need to be taken with a grain of salt. But I think it illustrates what I'm trying to say that arbitrary thicker or thinner isn't necessarily better without numbers to back it up. Obligatory YMMV and DYOR
I also think there's a misconception about oil pressure and too much emphasis on it. Barring extremes, flow tends to be a more important metric than pressure, as pressure can be manipulated viscosity. Sure you can run a 10w60, peg your pressure gauge, and claim pressure is good. But pressure is just a resistance to flow. If you put a thicker fluid in there, certainly it will resist flow more and give an increase in pressure. But, and here's the big "but" I think is missed; Your oil pump has a pressure bypass valve. Stray too thick, that valve opens, and despite higher/"better" pressure, your oil flow rates through the engine are cut down.
Now, with all this said, there's a Goldilocks zone as far as appropriate oil viscosity to run. Too thin, and it'll run through all the holes inside the engine too quickly. Bearing tolerances, bearing width, oil hole flow diameter, lifter bleed off rates, oil control ring design, and oil pump flow need to be calibrated to a given viscosity. There needs to be enough resistance to flow so that oil can make the appropriate loop through the engine. (If this bit isn't clear let me know, I'll expand on it). Likewise, too thick and you won't get enough flow to replenish things like bearings and piston wall coverage between rotations.
Being that temperature plays such a large role in viscosity, whether 15w40 is appropriate really depends on your climate and drive style. If you're somewhere hot and working your rig hard towing or doing something else that would raise oil temperature (and lower viscosity), then yes it's probably appropriate. If not, then I might give it a second glance.
For better or for worse, you'll need to run your OCI out and get some analysis done on it to figure out what's appropriate for you. This fellow here played with some 0w20 and 0w40 in his rig and found that the 0w20 posted better wear numbers than the 40 weight did. https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/4382069/Thin_or_thick_(TGMO_0W-20/M1_0
Now that's a different engine and the conclusions need to be taken with a grain of salt. But I think it illustrates what I'm trying to say that arbitrary thicker or thinner isn't necessarily better without numbers to back it up. Obligatory YMMV and DYOR
thanks for the replies. Just to be clear, im not talking about wanting to run that URSA 15w40 in anything. Im just wondering if there would be any effect on engine longevity, good or bad, from them having run the thing on it for 125k. If I were to buy it, thats certainly not what I would run in it
Might want to get an oil sample and send it out for examination for impurities and/or metal in it before buying.
iamdub
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Being a fleet vehicle, they probably used that so they'd only have to buy one type of oil in bulk to run in all their vehicles whether it had a diesel or gas engine.
I don't think it would've done any damage to the engine, but it may have shortened the life of the catalytic converters due to the higher zinc content.
If it's clean, priced right and well-maintained otherwise, I wouldn't be concerned so much and would switch to a high quality gas engine synthetic. Also, expecting another 100K out of a Gen3 with 125K well-maintained miles is undershooting. Take care of it and you could get 150K-200K out of that engine.
I don't think it would've done any damage to the engine, but it may have shortened the life of the catalytic converters due to the higher zinc content.
If it's clean, priced right and well-maintained otherwise, I wouldn't be concerned so much and would switch to a high quality gas engine synthetic. Also, expecting another 100K out of a Gen3 with 125K well-maintained miles is undershooting. Take care of it and you could get 150K-200K out of that engine.
SnowDrifter
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Ahh I misunderstood. I guess it really depends on the climate where the vehicle was located.
I'd give the thing a solid inspection and go from there. Paying close mind to hot oil pressure, piston slap, and lifter noise. If the seller is patient, see if you can send off an oil sample prior to purchase. Assuming he didn't just change the oil of course.
Oh, and hot oil pressure on these rigs needs them driving for 20-25 minutes. Oil temp lags HARD behind coolant temp.
iamdub
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I meant 150K-200K more out of that engine.
