only uses oil in town

[Clevy]

Originally Posted By: Chris142
Ida guessed the thick oil in town would burn less than hot thin oil and 3000 rpm.


No kidding. That is a mind exercise for sure.

Originally Posted By: Gokhan
Rings/cylinders are hydrodynamically lubricated, which means they wobble during their cycle. Wobbling increases with decreasing RPM and/or increasing engine load. When wobbling increases, it will decrease the minimum oil-film thickness, which will increase the pressure rise within the oil film. This higher pressure rise will result in increased oil consumption, as the wobbling motion will pump more oil by the rings.

You're keeping your engine at a high RPM in highway driving and I am guessing you're not driving too fast. So, the load on the engine is not high and the RPM is high and the wobbling is minimal. If you decreased the RPM (lugged the engine), wobbling and oil consumption would increase.

In city driving, RPMs are usually lower and the load on the engine could be higher as you accelerate, which could result in increase wobbling and oil consumption.

Switching to a thicker oil increases the minimum oil-film thickness and decreases the wobbling but since 15W-40 is already practically as thick as it gets, there is no further remedy.

(Note: I don't expect the oil consumption by the valve stems to depend on RPM or engine load much, as it's mostly determined by the valve-stem-oil-seal oil metering and/or valve-guide clearance.)



Wow. That explanation certainly covers all the bases.

Nice

 

[Shannow]

http://download.ms-motor-service.com/ximages/ks_50003958-02_web.pdf

Page 28 ?

 

[Jim Allen]

Shannow: Ahh, low speed and idling creates less sealing pressure on the rings. Same thing could happen with stick rings but I would think in that case the problems would be universal.

Chris: I live in a very rural area of Ohio. The nearest "big" town is 12 miles away and has a population of 5500. The small WalMart there carries the Rotella T5 10W30 for $16 gallon. If your nearest doesn't have it, they can get it. You've thrown more expensive oil than $4/quart at this problem and just about the only one you HAVEN'T tried is 10W30. You will not know until you try.

Beyond that, unless you intend tearing into the engine, you may as well live just with the oil consumption, using the cheapest decent oil you can find, or get rid of the truck. I have my doubts that 10W30, or any oil, is going to help much. If you are mechanically inclined and limber, the VS seals can be done without pulling the heads. Not sure what a shop would charge to do so. Some are loathe to do them without pulling the heads because if the valve guides are badly worn, the seals won't last long. It can be tough to get a good "read" on guide wear without having the heads off.

 

[bullwinkle]

Jim-I put one of those stick-on Wolverine pan heaters on mine and it made a HUGE difference in cranking speed. Stumped on the OP's problem as well.

 

[Chris142]

Ya i have done seals on gassers with the heads on.hopefully thats all it is. Or my 80k 6.9 is sick but it starts and runs fine. Btw the 5w40 was on clearance so i didnt pay much for it. Iirc it was $10 a gallon

 

[Gokhan]

You could try to do a compression check if it's possible. I don't know the procedure or specs for your engine but here is the procedure and specs for the diesel-engine version of my 85 Corolla from the OEM repair manual. It could probably tell you if you have worn rings or cylinders: