10W-30 better MPG than 10W-40?

Messages
233
Location
Pullman WA
I've got a 87' mazda 2.0 engine with 143,000 miles on it (B2000) my last change I went with chevron supreme 10W-40 and ST oil filter (I average 24 MPG in town. 28 MPG highway). Will switching to a 10W-30 increase the MPG at all? I'm open to suggestions, I'm considering 10W-30 high mileage oils, aka castrol/pennzoil..Thanks
 
Messages
2,908
Location
Georgia/Retired
Theoretically you should see a fuel economy increase but based on my own personal experiences there are too many other variables involved in calculating fuel consumption to realize a noticeable difference with only this change. (How's that for a run-on sentence [Big Grin] ) I have gone from 0W-30 to 15w-50 in my 2.5 liter 6 cylinder car and I didn't have any noticeable change. Things such are climate, road conditions, lunar magnetism, and belly button lint seems to have as much impact as the oil viscosity. edited to correct viscosity. [ September 13, 2003, 10:48 PM: Message edited by: FowVay ]
 

CJH

Messages
489
Location
Pennsylvania
So often I read people on here say they are using very light oils to get more mpg or more HP. I have to think they are trading off engine reliability for an improvement that is neither noticable or measureable.
quote:
Originally posted by FowVay: Theoretically you should see a fuel economy increase but based on my own personal experiences there are too many other variables involved in calculating fuel consumption to realize a noticeable difference with only this change. (How's that for a run-on sentence [Big Grin] ) I have gone from 0W-30 to 15w-50 in my 2.5 liter 6 cylinder car and I didn't have any noticeable change. Things such are climate, road conditions, lunar magnetism, and belly button lint seems to have as much impact as the oil viscosity. edited to correct viscosity.
 
Messages
36,108
Location
ME
I'd put synthetic gear oil in the rear end and tranny. You'd be set for 30k miles at least so the cost is amortized over a long time.
 
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