Have '88 420 SEL w/163K that runs exceptionally well.
For the last 3K miles, I have been running on 20W-50. Went to this based on the conventional wisdom that a high-mileage V-8 needs the heavier oil, especially in steamy South Florida.
The 20W-50 exhibited these characteristics: I perceived some increase in low-end engine power and acceleration. However, produced different engine sounds and some higher end vibration (almost imperceptible). I consumed more oil w/20W-50, but no decrease in mpg. Also, smelled more exhaust fumes w/20W-50.
Well, recently I rad a post that the 10W-30 (or lighter oil) will more quickly lubricate the top end of the engine at start-up, particularly after sitting overnight, etc.
So- I just switched back to 10W-30. Engine sound differed-and no vibration. No smells, either. And I might be imagining this, but a slight loss of low-end power compared to the heavier oil.
What do you guys think? Should I stick to the 10W-30?