Low Oil Pressure: OW-40 OK?

On what basis? Experience for one, and common sense for another. The manufacturers admitted even then the low viscosity oil was STRICTLY for C.A.F.E. reasons. Every 10th of a MPG they could gain in fuel mileage was a HUGE bonus. In the 10 years I spent as service manager at a very successful Toyota dealership, we NEVER had an engine failure of any sort on vehicles we serviced regularly. Not a camshaft, timing chain, or engine bearing. NOT A ONE.We serviced over 600 vehicles on a regular basis and had about 1000 on "active" status on the cards. Many went well over

300,000Km. Yes, we had the occaisional head gasket issue, particularly on the "T" and "M" engines. No oil under the sun could prevent(or cause) them. Yet I had many vehicles in for engine work that were sold and serviced by the other dealers in the area who slavishly followed the "book". "M" series camshafts, timing chains and tensioners," R" series timing chains and the odd oil pump, and the occaisional bottom end. "S" series timing chains were just starting to require replacement when I left The service rep asked me why our warranty instance was so much lower than the other dealers and I told them what we were doing. He said they'd get skinned alive for recommending it, but it was undoubtably the best practice for engine longevity. The oil was changed 4 times a year - 20W50 went in from March 1, more or less, 'till roughly September 1, and we used 10W40 the rest of the year. My brother had the same experience at a Ford dealership with Pinto, Mustang, Ranger and Aerostar 2300s. With 20W50 summer oil they never had a camshaft failure -nor did the dealers in the south using 20W50. With the recommended oil camshaft failures were not uncommon and the factory reps were telling the dealers they could not officially say it

- but running 20W50 in the summer, particularly south of the Mason Dixon, was really a good idea on those engines.

The lifter problems that plagued the 230 and 250 inch Chevies on 10W30 were significantly less common when the heavier oil was used, as were the camshaft failures on Chevy 307s. The rocker ball wear on Ford 351 C and M engines was a lot less common with thicker summer oil as well.. And that was back when both oils still had Zinc and Phosphorous EP additives.

Reply to
clare at snyder.on.ca
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It idles at 800 RPM. So at 900 it is right at 15 PSI. I'll switch to the

0w-40 and see what happens. I'll report the results.

Reply to
Scott Buchanan

I'm sorry common sense and experience are really bad ways to make important decisions in life like changing oil. Forget all that nonsense. You need to start Googling for answers. For instance, with a little searching you might find a site by "Bob the oil guy" that will set you straight. A little more digging and you can find some guy who brags he's blown up 50 engines in his career. Obviously this guy knows what he's talking about when comes to severe duty service. C'mon you got do better than your own common sense and experience.

-jim

Reply to
jim

And I run 10w30 on everything I own from a 1966 to a 2000 (the manuals on the later ones call for 10w30, the '66 still references single-grade oils but I use 10w30 anyway) and can make the same claim. Two of my engines have exceeded 350,000 miles. Yer point?

I know of *quite* a number of engines that will develop enough oil pressure when cold on 20w50 to put the spin-on filter at risk of bursting.

Besides, thick oil boosts pressure but flows WORSE inside the engine so that its not actually reaching the critical contact points. Viscosity has almost nothing at all to do with actual film strength. There are

0w30 oils with better film strength than single-grade 30-weight.
Reply to
Steve

Had a similar situations with a 4.3 S-10 Blazer at ~180K miles. idle oil pressure poor with 5-30, but fine with 20-50 or 15-40

I'd go with 15W-40 oil for diesel engines (Delvac, etc) you have 150K on it, lots of wear and lots of slop. Oil intended for diesels has a load of anti-wear additives in it....at this point you're trying to get max life out of the motor before rebuild, not max economy, right?

likely, your rings have some wear and your oil is being diluted (with gasoline) over time, too.

Plus, 15W40 comes in gallon or 3.8l bottles and is reasonably priced vs 20W50 which is becoming a specialty item in some areas, anyway

Be sure you have GOOD PCV function, this will help to reduce the dilution effect.

My opinion...flames welcomed and ignored...

--Don Don Byrer KJ5KB Radar Tech & Smilin' Commercial Pilot Guy Glider & CFI wannabe kj5kb-at-hotmail.com

"I have slipped the surly bonds of earth; now if I can just land without bending the gear..." "Watch out for those doves..."

Reply to
Don Byrer

This is a misunderstanding. A 0W-40 oil will be thicker at operating temperatures than a 10W-30. The upper number references viscosity when hot, the lower number refers to pumpability when very cold.

Reply to
John Horner
0W-40 is a thinner oil which will lower your oil pressure. You want to use a thicker oil like 10W-30 or 20W-50. -------- Mike.

This is a misunderstanding. A 0W-40 oil will be thicker at operating temperatures than a 10W-30. The upper number references viscosity when hot, the lower number refers to pumpability when very cold. --------------- John Horner.

What is the difference between pumpability and viscosity? --- Rodan.

Reply to
Rodan

Nothing really, except it is inverse. High viscosity is low pumpability. Viscosity is basically thickness.

the number before the W is the cold viscosity - measured at 0F IIRC. Might be colder than that. The number after the w is the hot viscosity. Wide viscosity range oils have had a bad rap for loosing viscosity when hot after prolonged use.(due to polymer shear) but unless you are running extended drain intervals(which I do not advocate) ther is nothing wrong with a quality 10W40 oil.

Reply to
clare at snyder.on.ca

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