Low Oil Pressure: OW-40 OK?

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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.
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clare, at, snyder.on.ca wrote:

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

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On 29 Nov 2007 09:27:59 -0500, snipped-for-privacy@panix.com (Scott Dorsey) wrote:

The "low oil pressure" lights don't come on until about 4PSI, so 12 is NOT an issue.
GM got around this kind of problem by making their pressure guages "dummies". On my 3.8, the oil pressure always reads mid scale unless it reads zero. They use a backwards oil pressure switch with an inline resistor.
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I've had two cars that were even lower at idle. Both were high mileage and both went another 50,000 miles like that and were still running when I sold them. Easier cure it to put a little piece of duct tape over the lower portion of the gauge so you don't see it.
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I would just use the oil recommended for your car. I don't see how 12 psi at idle is a problem. But what does the tech manual for that engine say.
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Good question. I looked that up. The one section does state that the low pressure indicator is to show at 4 PSI. The engine specification section states 15 PSI minimum at 900 RPM. I don't know what the actual idle speed is but it is close to 900. I'll check it when I drive to work today.
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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.
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On Wed, 28 Nov 2007 09:12:02 -0300, "Scott Buchanan"

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...<smack-smack-smack-smack...>"
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