What could the problem be?

[mkiiisupra]

Originally Posted by Busted Knuckles

mkiiisupra, I beg to differ on a few points.

Point 1: 20W50 is a recommended oil for the 7M-GE and 7M-GTE for ambient temperatures above 40 deg F, according to the owner's manual. So, the oil journals, including the cam journals, are sufficient for this viscosity. I live in Atlanta, and we only see temps below 40 for a couple of weeks in the dead of winter.

Again the following from jdub over at supramania.

Note that 20W-50 is listed for a 10 to 100+ F temp range...so is a 15W-40 and 20W-40. On the 2nd line a 10W-30, 10W-40, and 10W-50 are listed for 0 to 100+ F temps...a wider temperature range. Also, if you look at the verbiage at the top, the manual shows API grades SF, SF/CC, and SG...all are obsolete API grades...you cannot even buy these oils anymore. The current API grades are SL and SM...these oils represent a quantum leap in formulation improvements over the oils available when the Supra manual was published. Modern oil's at SAE viscosity 0W-20, 5W-20, 0W-30 and 5W-30 easily cover the temp ranges (especially in cold climates) most of us operate the motor at...oils have simply improved that much over the last 20 years. Bottom line: Take the Supra manual oil chart with a grain of salt.


The manual recommends it - False
See above. The manual does not specifically recommend a 20W-50...it's just one of the oils listed that are "approved". It also recommends a 10W-30...an oil that covers a wider temp range. Completely ignores that API SF and SG grades are obsolete.