Spring00gt

Why is it bad to switch a high mileage car from regular oil to synthetic oil???

sweet99

It's not in my opinion. Mobil 1 makes a heavy weight synthetic if that is the reason some will say. 20W-50. Even a 40 weight should be fine. Call 1-800-mobil-on and ask them!

cliffyk

There's nothing bad about it per se', however you may find that engine seals that were only "misting" on dino oil will weep or leak with synthetic (it has smaller molecules and can get past sealing surfaces that are able to hold back dino oil).I have had this happen on two of the half-dozen or so vehicles I've tried to switch to synthetic, on both going back to dino sealed things up again.[/align][/align]However, there is no real advantage to switching a high mileage car (or any car for that matter) to synthetic oil, as long as you buy quality dino oil and change it every 2500 to 3500 miles. [/align][/align]I run 10W-30 synthetic in my Mustang because that's what was in it when I got it and it only has 60k miles on it, everything else we own (all with 150k+ miles) runs on Valvoline Maxlife 20W-50 (Florida=hot!). When the 'stang starts using oil and/or reaches 120k miles or so it will be living on the Maxlife as well.[/align][/align]

sweet99

Switching to synthetic will actually add about 5-8HP! I have heard about the seal thing but never experienced it myself and have a friend using synthetic in 60's vehicles for the additional power. Go ahead and switch if you haven't and are just asking the question but you can call mobil and they will explain all you want to know about oils.

mustangman02232

uhhh no it wont

i run blend just for the simple fact that i drive so much, all these oils have all these additives and all kinds of **** and it really doesnt make a differeance unless your boosting or have over 200k on the clock

20-50 is a bit extream however thats desiel oil

Fobra

synthetic will actually free up some power... but i doubt that much... synthetic does offer better protection, esp in the case of a pressure drop, it might buy you another few secs

2000GT4.6

It might not make that much, but syn will definatly show a power increase. Syn>blend>dino oil

After seeing the results on my car (oil looks new at 3k, car takes x2 as long to heat up) I will never run anything but full synthetic again. On any milage car its just better, plain and simple, so long as it isn't acutaly using oil.

GhostRider02GT

M1 makes a high mileage synthetic oil

StylinM6s

On royal purple's site under why use royal purple. It states "Increases horsepower and torque by as much as 3%" which I can actually believe though

livefast1

its only gonna give u an unoticable amount of horsepower because like stated above its molecularly thinner which creates less drag on the rotating assembly. but i run AMSOIL so synthetic FTW.