Is it just me?

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Staff member
Dec 14, 2002
New Jersey
is it just me, or do others' cars seem to feel like they have a bit less power at full operating temp when using 5w-40 instead of 5w-30? My truck only has 34K miles, has had oil changed every 3k, sometimes synth (mobil1) sometimes dino (pennzoil or GTX). I dont think the engine is dirty or sludged up. But it does feel a bit weaker. Is it me, or am i onto something? Thanks
No it's not you, it is the heavier oil. You will loose a few hp.
A lot of it is mental I believe. I've previously seen dyno tests where an engine is switched from 20w50 to 10w30 and picks up 3 or 4hp. But you honestly won't notice 3 or 4 hp difference in the seat of the pants meter. Going from even a thin 30wt to a thick 40wt should not even be much more than a 2hp difference, tops.
Noticeable loss of power?...probably just the engine running quieter with the heavier oil. Ken [ March 23, 2003, 07:54 PM: Message edited by: Ken2 ]
Yes, the car will seem sluggish. This will only be temporary (few thousand mi.) until the thicker oil cleans out/displaces the crap that formed because it was able to with the thinner oil used. At least this is what I found...
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