Not one North American car company recommends or has recommended 10W-40 for
years. The excessive viscosity index improver was implicated in excessive
varnish production resulting in stuck and cracked rings.
This is ONLY a problem with extended drain intervals, andin my 1988
Chrysler manual under lubrication, indicates 15w40 is the preferred
oil for operation above 10 degrees F.
The "range" of 5 w 30 oil is the same as 10W40, and uses the same
viscosity improvers. I have had more problems with cheap crap grade
10W30 oils than any other. You know the stuff you get at the
drivethrough oil change place, complete with the fram or Penzoil
filter for $9.99.
The 10W40 and 15W40 oils are generally only available in the premium
oils. Ditto for 20W50.
Now for some experience. Remember when the Ford 2300 engines in the
Mush Stang 2 was having camshaft problems, particularly south of the
Mason Dixon Line???? They fairly quickly found that running 20W50 oil
in the summer, and 10W40 the rest of the year totally eliminated the
camshaft problems. TOTALLY. Not ONE failure in the test group running
20W50 and 10W40, vs a fairly high percentage with the recommended
5W30.
Toyota 3M and 4M engines in Crowns, Mk2s, Cressidas and Supras were
having problems with camshafts and rockers under warranty in the late
seventies and early eighties. The warranty service rep asked how we
had managed to get away with NO camshaft and rocker replacements under
warranty, while the dealer accross town was doing a couple a week -
and we were selling as many, and servicing more, than they were.
I took him to the oil barrel and showed him.
I NEVER used 5W30 oil, Never used 10W30 oil.
From April on, the tank was filled with 20W50, untill Sept /Oct when
it went to 10W40.
Not only did we not replace cams and rockers, I could likely count on
the fingers of one hand how many bearing or timing chain problems we
had in 10 years - servicing over 600 vehicles a year.
Remember the 2600 cc Mitsu Shitty "Hemi" in the early Dodge
MagicWagons??? That 6 foot long timing chain with the crappy
tensioners???? 10W40 and 20W50 oil, changed 4 times a year, made them
last hundreds of thousands of Kms. Without sounding like a cement
mixer. Never saw one using the heavier oil seize the balance shafts
either - saw more than one running 5W30.
Know something? Didn't have the sticky ring oil burning problems
either.
C.A.F.E. pretty well mandated the recommendation of low viscosity and
"friction reducing" oils.
Chrysler is covering their ass saying not to use 10W40 oil because of
the "politically correct" decision to recommend 12000 Km (7500mile)
oil change intervals.
The "extreme" or "severe" operating condition schedule is 3 months,
3000 miles - and in that time period shear failure of 10W40 oil is a
total non-issue.
Use any major brand oil of the proper quality grade in the venders
recommended viscosity. 5W-30 in cold weather is usually preferred and 10W-30
in other conditions works well in that motor.
If you want to stay within Chrysler's recommendation, you can't go
wrong with 15W40 Rotella changed 4 times a year if operating temps do
not go below 10F.
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