Motor Oil

[stangman16]

I have a '99 Mustang GT that has about 75k miles and it's had Mobil 1 5w-30 all it's life, and a friend has been telling me I should go 5w-20 Motorcraft. What are your thoughts and opinions on this ? I kinda don't want to switch oils because it's had the same oil brand all this time, but I'd like to know if switching to 5w-20 (which I believe was recommended) will cause any leaks or whatnot since I've been using 5w-30 ?

 

[BuffaloZone]

I have a '99 Mustang GT that has about 75k miles and it's had Mobil 1 5w-30 all it's life, and a friend has been telling me I should go 5w-20 Motorcraft. What are your thoughts and opinions on this ? I kinda don't want to switch oils because it's had the same oil brand all this time, but I'd like to know if switching to 5w-20 (which I believe was recommended) will cause any leaks or whatnot since I've been using 5w-30 ?

Going from Mobil 1 to the 5w-20 Motorcraft would be my 1st choice. More like going from Mobil 1 to Amsoil.

 

[03ghoststang]

you should just continue to use it if it's not leaking then just keep using it like iv'e been using 5w-20 since my car was new so just use what you have on

 

[helty]

ford began recommending 5w-20 over 5w-30 a few years back because of CAFE. some emissions or fuel mileage crap. i say keep using what you have been.

 

[40th GT]

I've switched from Mobil1 5w-30 to 5w-20 on my 04 and my average MPG around town increased from 18.3 to 19.6. Yeah yeah, I know the temperatures could have been varied a couple degrees and such but my overall driving style was the same. I don't want to start an argument so take it with a grain of salt and you can always try this yourself if you're curious.

And my engine doesn't use any oil with the thinner weight. But then again my engine only has 8000 miles, so I'd be kinda hesistant to use it on a 75k car.

 

[Kilgore Trout]

For that car I would stick with the 5W-30.

 

[stangman16]

Cool, thanks - I figured 5w-30 would be sufficient enough for this car, it's only my daily driver and not my race car. The race car has about 3 years left of work to it... but it's a fun ongoing project!

Thanks for the replies!

 

[sgarlic]

Whatever the thinnest oil you can use, and still maintain adequate oil pressure (which you won't know unless you use an aftermarket oil pressure gauge anyways,) is what you should run.

I'll run Mobil 1 5w20 til I can't hold hot idle pressure, then I'll probably swap to 5w30. Higher mileage you may need the 30 to keep it up. My foxbody runs 10w30 with 130k fine, my wife's Jeep at 170k needs 20w50.

 

[stangman16]

which you won't know unless you use an aftermarket oil pressure gauge anyways

Do you know why that is? I noticed in my '66 that oil gauge is useless as well... guess they haven't changed it much in 39 years.

 

[sgarlic]

Do you know why that is? I noticed in my '66 that oil gauge is useless as well... guess they haven't changed it much in 39 years.

I'm not positive, but I would suspect it is one of 2 things:

1) Ford found it was more cost effective to use dummy type gauges during the manufacturing process. You have to figure, with dummy gauges, they can just pretty much apply power to the cluster, set the needle position, and be done with it vs having to calibrate each needle...

or

2) Ford figured if they put fully functional (fluctuating) gauges in a brand new car, owners would be bringing it in every time the oil pressure needle went down, or the temp needle went up on a hot day in a traffic jam, etc.

 

[Gearbanger 101]

Run whatever is on sale at Pep Boys. Some of you guys just put too damn much though into engine oil. You'll never notice a difference from one to the other. Change it regularily and rung a quality filter and it will last as long as any of the guys running the high dollar stuff!