Mustang GT (5W-20) Synthetic or Dino?

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Apr 23, 2003
The Bay Area

I'm breaking in a new Mustang GT (4.6L V8). The factory suggests that I use a good quality 5W-20 weight oil. I was thinking of running 5W-30 Mobil 1 for 3,000 mile intervals, but I am worried about seepage.I would like maximum protection, not maximum leakage. I had a 01 F-150 with the same ltr. size motor. I had two HG leaks fixed at 19,500 miles. Could it be the Red Line oil I was using? I know that cars and truck typically aren't supposed to leak.

Should I switch to syn.?

should I switch viscocity?

What is you opinion?


*PS does Mobil 1 make a 5W-20? If so, where can I pick up a couple of bottles?
If you are going with 3000 mile intervals I would stick with dino. You could go with Pennzoil, Chevron Supreme or any quality dino will do at 3000 mile intervals. You can go with the synth but IMO you are wasting $$$$$ if you are changing it at 3000 miles!
I would go with 5-30 if your warrantee allows it.

As far as leaks go I don't think its the oils fault there. If your vehicle leaks with synth and continues to leak you need to switch back to dino.

Daily Drives
-2003 Toyota Tacoma PreRunner XtraCab, Impulse Red, Peppy 2.7 Liter 4 Banger, Running Mobil1 Synthetics SS 5W-30.
ODO 4000 Miles.
-1995 Toyota 4-Runner, Evergreen, 3.0 V6, Running Mobil1 Synthetic SS 10W-30.
ODO 78000 Miles.
Hey mf150,

start out with a good quality 5w20 oil and let in break in for about 500 miles, change the oil and go straight to synthetic of your choice. Now on the cleaning part @ 500 miles I"m not sure if that's necessary bu it couldn't hurt either. Seems like the newer cars of today require a less "baby" like break in period. When I say "baby", means you don't really have to drive like grandma, nowadays just drive like normal and don't do anything stupid

After the break in period, you can go to synthetic but 5w20, mmmmmmmmmmmm, it might be too thin but yet my grandma has a 2002 Taurus that calls for 5w20 and it runs fine with the 5w20. Anyway, just my $.02
sup mf150,

BTW, nice car

Start out in the break in period with a good quality dino oil, Motorcraft, Valvoline etc.. in the 5w20 or 5w30, neither will hurt. When it hits the 500 mile mark, get that oil changed and from there I think it's safe to say you can go to synthetic. I've heard some guys go to synthetic at 800 miles without a problem. As far as cleaning it out prior to synthetic, I would do it so you can all those little metal particles and such outta there but then again it might not be necessary, I"m still a rookie here
Your choice of synthetic is up to you or if you decide to stick with dino, that's cool. Amsoil, Mobil, Redline, all good top notch synthetics. AS far as dinos go, Scheaffer(sp?) uuuuuuuhhhhhhhh, there's others out there just not familar with them, I guess I"m just a synthetic kinda guy
But yea man, congrats on the stang,,,,,AR
Redline has little to do with the leaking head gasket issue on some of the 4.6 engines. A combination of poor blocks and a bad gasket design (the old aluminum head/iron block issues rears its head again) causes the problem on affected motors, not motor oil choice. Fact of the matter is that no properly formulated synthetic oil will cause "leaks or seepage". Period. If you have a leak with a synthetic, you would have had a leak with the dino oil too.

If you are doing 3,000 mile intervals, forget using a synthetic unles you like throwing money out the window. A decent dino oil, in 5w20 or 5w30, from Penzoil, Chevron/Texaco, or Motorcraft would be a fine choice. I'm sure you are aware of the warranty issue and lubricant choice, so I'm not going to harp on it. That's whatever you are comfortable with. We all know that the 5w30 is fine in these mod motors, and the 5w20 is looking pretty good so far.

Mobil 1 does not make a 5w20 and has no plans to. 0w20 is the recomended grade for vehicles that require it. By definition, if an oil qualifies for a lower cold grade, it meets those above it too - thus a 0w20 meets and exceeds the requirements to label the oil as a 5w20. The choice of marketing a 0w20 oil seems to me to be a bit of marketing in itself as a look, I'm better than 5w20.
AR- Thanks for the support! It's a wonderful car. I just switched from a full size F-150, so the handling and pick up on the mustang is impressive.

MNGopher- I wholeheartedly agree that the oil does not cause leaks. Red Line is a victom of bad associations. Is Red Line API certified (I've witnessed how well it lubricates). Do you think the PolyolEster basestock is superior to the PAOs used in Mobil 1? Do you think Red Line will make a difference in engine longevity? I'm not into racing, but I do live in a city with lots of congestion and stop-n-go driving.

Thanks to all for your responses!

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