Does Oil Weight Affect Mpg?

[Spenceeros]

I have a 92' pathy with about 220k on it and I decided to put this high mileage 10-40 mobil one in during an oil change. Now I do notice a pretty big decrease in gas mileage. I'm not sure if its just coincidence of my car getting old or if the -40 weight is too heavy for the older engine. And yes I know a lot of people look down on using synthetic in older cars, but it so far has been working out for me.

[Toby]

Probably too heavy of an oil. i ran synthetic in my 94 Camaro.

[MY1PATH]

stick with 10w30 and 5w30. It does make a differance. the reason synth is frowned upon w/ older engines is because it has a greater potential to leak. If your seals are holding up fine when you use synth and you don't seem to be losing any significant ammount between changes then your fine. If you develop a leak you can compromise with blended synth and see if that helps b4 going full dino oil.

[Toby]

stick with 10w30 and 5w30. It does make a differance. the reason synth is frowned upon w/ older engines is because it has a greater potential to leak. If your seals are holding up fine when you use synth and you don't seem to be losing any significant ammount between changes then your fine. If you develop a leak you can compromise with blended synth and see if that helps b4 going full dino oil.

 

Yeah one of the problems too is it starts breaking down the old gunk and sometimes that's the only thing that's keeping the gaskets from leaking in the first place.

 

i'd much rather use synthetic.

[SamTex]

Probably too heavy of an oil. i ran synthetic in my 94 Camaro.

 

You sure love that old Camaro.....

[Toby]

You sure love that old Camaro.....

 

I do. I wish I still had it. Probably the best car to date I think I've ever owned. Most comfortable next to the Pathfinder and Suburban.

 

I miss it.

[Spenceeros]

Great, Thanks for the info. I am starting to suspect that it might be a bad cat converter too.

[YoungWheelsCT]

yeah before finding my pathy i too rocked a camaro and it was very comfortable but i am now a pathfinder kind of guy

[jbdevega]

Yes it has a huge difference, biggest point i can make on this is my maxima. my maxima on 5w-30 gets about 29.5 mpg, while on 0w-30 gets 33.5 mpg. I was advised by alot of people not to switch to 0w oil because it would leak everywhere. well i lucked out and it didnt, parcially due to the fact that it has been running on high mileage durabled oil for the last 100k miles. If you really want to switch to full syn oil i suggest you use high mileage durabled oils for a little while they contain addatives that will renew your seal to keep them from leaking when you start to use full syn. I ALSO HIGHLY RECOMMEND A ENGINE FLUSH IF YOUR STILL USING CONVENTIONAL OIL!!! i cant describe the number of times ive seen a guy switch from conventional to durablends or even syn, and all it ends up doing is dislodging a ton of sludge in the engine, then it really kills the engines power.

[adamzan]

I switched from conventional oil to synthetic and it runs great. I've see as high as 23mpg on the highway in the summer with 5w30. No way in hell I would put 0w30 in my pathfinder.

[JesseLivingston]

old camaro? my mom had a camaro, it was the first car i drove! first car i did a dougnut in, first car i wrapped the speedo around in, absolutely no suspension, but nothing could keep up in the corners... unless it was raining, or even a little damp! i can still remember that suttle growl in the engine. I think i got to go get one!