Originally Posted by harbor
Sonoros - Give me some more detail on this please. My owner's manual lists 5W-20 engine oil as an acceptable replacement fluid, as long as it meets API SL or GF3.
If you've had problems, let me know so I can replace my fluid.
The same verbiage "API SL or GF3" is used in virtually every single US auto manual and/or repair guide. That's just a measure of its resistance to heat. What matters for tranny fluid is also its shear viscosity under extreme pressure, for which engine oil is unrated.
How I know from experience - I only drive MT cars and did my first 5MT fluid swap on my brother's DC2 Integra @ 140,000 miles. We pulled out his owner's manual from 1995 and indeed, it specified synthetic 5W-20 engine oil meeting "API SL or GF3" specs. We drained the fluid and refilled to spec with engine oil. Immediately afterwards, he complained of poor shifting. I verified. Gears were grinding on shifts, the gearbox felt notchy.
After 3000 miles, we completely drained the gearbox, refilled with 08798-9031A, and the shifter felt better than new. I'm talking about S2000-style gearbox performance. Completely transformed. The change was instantaneous by the way. The instant the new MTF was put in, the shifting performance was restored.
Engine oil = bad. You may also try GM Synchromesh semi-synthetic with Friction Modifier, #12377916.
I still think the Acura fluid is the best.