Should I have changed my oil?

We were talking about getting oil changes at work and when to put heavier oil into cars as they age. It seems that most people think I am wrong by having high mileage cars and still running the same thin oil the factory calls for. I know it used to be common for an older car to get thicker oil but I assumed that had to do with a particular need like consumption or dripping. I figured as long as I am not burning or leaking much oil between changes I am good with the 5w-30 it says on the cap. Am I missing something?

I'm with you. If it's not burning or dripping, why switch to thicker oil?
That being said, I've owned enough british cars and german diesel cars that I switch to thicker oil by habit.

I don't think you are missing anything. I'm still with the same 10-30 in my +200k Miata- actually considering using the thinner option of 5-30 in the winter, the more it ages. As long as the bearings are not making noise- they are as close as they need to be to use the oil. Heck, iirc, Per wrote a nice oil article, which strongly suggested that most racers use too think of oil, and for autocrossers, it could be costing them power.

Where did the "most people" get their tribology information from?

If you still have good oil pressure, don't bother.

If you're burning oil, next time you add a quart, add a quart of Dexron. It's amazing how often that will clear up sticky rings. It doesn't help worn valve guides/seals, but most oil burning problems are the rings. (If you are REALLY burning oil, next oil change, add four quarts of it and run it for 3,000mi. Worst case scenarios is that it doesn't work.)

Modern engines wear very little. Credit stiffer construction and EFI. 200k+ engines can and will have bearings that look like new and bores that are barely worn except for a light fading of the cross-hatch where the piston skirt rocks over at TDC.

150k on the Avalanche and still the same 5w30 called out in the service literature since we got it at 55k. I've even done 0w30 and 0w20 in it for MPG experimentation.

I think the 128k mile Dakota calls for 10w30, but I run the same 5w30 as my other vehicles.

No reason to run anything thicker then 10w30 anymore on something made within the last 20 yrs. If I had a fresh motor, I would be running a bearing clearanced for it, 0w10.

I just use that high-mileage stuff in the factory-recommended viscosity for my '93 Toyolla. Although it does burn through about a quart of oil ever 1,500 miles. So maybe I should try 15W-40 instead of 10W-30?

My Mustang calls for 5W-20. I dump 10W-30 in it because I run it hard.

The longer you use thinner oil which gets to cold engine parts faster on startup, the longer it will be before you need thicker oil.

If you have a car with variable valve timing, you can actually screw them up with heavier oil.

Woody wrote: If you have a car with variable valve timing, you can actually screw them up with heavier oil.

In some cases. It depends on how the variable cam timing works. For instance, on the older 4.6L Modular Ford V8s, oil pressure is used to actuate the cam timing. So changing the oil viscosity would alter the pressure and thus could cause problems. The new 5.0L V8 doesn't use oil pressure for cam timing, however.

Heavier oil is actually tougher for the rings to scrape off the cylinder wall, and will sometimes burn more than lighter oil.

I used to run 0W-20 in my 200k mile CRX and it ran beautifully.

Sky_Render wrote: My Mustang calls for 5W-20. I dump 10W-30 in it because I run it hard.

That makes no sense.

Javelin wrote:

Sky_Render wrote: My Mustang calls for 5W-20. I dump 10W-30 in it because I run it hard.

That makes no sense.

Agreed. It should just be changed more often.

Streetwiseguy wrote: Heavier oil is actually tougher for the rings to scrape off the cylinder wall, and will sometimes burn more than lighter oil.

It can also be harder to get to the smaller, difficult to oil areas with a thick oil, exacerbating any problem areas an engine may have.

Javelin wrote:

Sky_Render wrote: My Mustang calls for 5W-20. I dump 10W-30 in it because I run it hard.

That makes no sense.

It does if your oil tempertures get high after a long period of WOT around a road course.

In daily driving, I run like 6 quarts of 5W20 and 2 quarts of 10W30. So it's like 6W22 or something.

Sky_Render wrote: In daily driving, I run like 6 quarts of 5W20 and 2 quarts of 10W30. So it's like 6W22 or something.

Am I the only one here with a car that states 4 different weights of oil depending on what the temperature is? That said, the explaination is completely in German and Celsius.

Ford spec'd 5W20 in the new Mustangs for CAFE reasons: they wanted a slight boost in MPG. Case in point: the "Track Pack" Mustangs have the EXACT SAME engine with the addition of an oil cooler, yet they call for 5W50 instead. So I add two quarts of slightly thicker oil for added insurance.

Sky_Render wrote:

Javelin wrote:

Sky_Render wrote: My Mustang calls for 5W-20. I dump 10W-30 in it because I run it hard.

That makes no sense.

It does if your oil tempertures get high after a long period of WOT around a road course. In daily driving, I run like 6 quarts of 5W20 and 2 quarts of 10W30. So it's like 6W22 or something.

Um, it really doesn't work like that.

What doesn't work that way? Mixing oil viscosities? Why not?

All of the oil is Mobil 1; I'm not mixing brands. According to Mobil 1's website (and others), mixing a thicker oil with a thinner oil creates an oil with viscosity characteristics between the two.

http://www.mobiloil.com/USA-English/MotorOil/Car_Care/AskMobil/Mixing_Motor_Oil_Viscosities.aspx

http://www.mobiloil.com/USA-English/MotorOil/Car_Care/AskMobil/Harm_Mixing_Different_Mobil_1_Viscosities.aspx

"... there is no harm in mixing different viscosities of Mobil 1."

This is fun. Next?

Furthermore:

""If you mix viscosity grades such as a 5W30 low-viscosity oil and a 10W40 higher-viscosity oil, it is reasonable to expect that the resulting product will have viscosity characteristics which are thicker than the 5W30, but thinner than the 10W40. ..."

http://wiki.answers.com/Q/Can_you_mix_motor_oil_viscosities

+1 for no need to run heavier just because it's old. You put heavier oil in it if it's burning oil or having low oil pressure around idle RPM.

yamaha wrote: Am I the only one here with a car that states 4 different weights of oil depending on what the temperature is? That said, the explaination is completely in German and Celsius.

Nope. My Trooper's manual does the exact same thing, for all 5 oil-containing devices on it!