I've used it in the summer on every vehicle I have owned since about
1973, except for my current Mystique and TranSport where I use 10W40. I generally put about 200,000 miles on an engine. Never had a lubrication related engine failure. Closest would be valve guide failure on 3.0 Mitsu - and they would fail regardless what oil you used. Chevy's and Pintos/mustangs (2300cc) back in the '80s that ate camshafts did NOT eat them with 20W50 in the summer.
2.6 Mitsus did not stretch timing chains on 20W50 - but you still had to do the countershaft fix, same as you did on 10W30 to get any life out of them. If you could run straight grade 20 on an engine without it being too thick for the conditions you can run 20W50 - and I don't know of a single engine on the market in the last 30 years that can not use straight 20 in the summer because it is too heavy. 20W50 is like 20 that doesn't thin out as much above 100F.
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.
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.
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.
Name 'em. I've only ever seen ONE split and that was through stupidity - -40 on
20W50 in a Slant Six.
And 20W50 is no thicker where it matters than straight 20.
0W30 Synthetics will quite possibly have better film strength than a straight grade 30 - but with conventional oils, the higher viscosity oils of the same quality will ALWAYS have a better film strength than the lower viscosity.
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..."
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.
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.
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.
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