I have used synthetic in my truck since I bought it brand new after it's initial 3k mile break in period. I used to just buy whatever synthetic was on special which was usually Castrol Syntec , Valvoline, or Penzzoil Platinum. I recently changed over to Mobil 1 Extended Performance and have seen about a 1mpg increase and smoother idle. However, when I waspouring the oil in I said to myself, "wow this stuff pours like water" I have since developed a crankcase seal leak.I have 25k miles and am still under factory warranty,. I took it in to the GMC dealer and had the seal replaced. I then drove it 1 roundtrip for 40 miles and the leak came back. I'm thinking that since it is such a longlife oil it has more detergent than the others therefore making it thinner even though it's rated at 5w30. What do you think Swartlkk and Lastcoupe? I need some expertise advice. Is it just coincidence or should I change back to standard Mobil 1 5w30 synthetic?

thanx

 

I originally had leak issues in my Bravada when I switched to Mobil 1. Not from the oil itself as I later found out. It was simply from loose pan bolts! Re-torqued the pan bolts to spec only to have them loosen up again later. I then went through and removed the bolts one at a time, cleaned the threads in the block and on the bolt and applied some oil resistant medium strength thread locker. Once I had them all tight and staying tight, the leak disappeared. I thought I had a rear main leak when this all started... The leak didn't have anything to do with the switch to Mobil 1 for me, it was just a coincidence.

And the M1 EP does have a different additive package, but I do not believe that they have higher detergent levels. Most of the EP oils have more wear inhibitors than standard drain oils.

Pennzoil Platinum has a pretty good following over at BITOG.com.

 

I normally used conventional Mobil Clean 5000 in my last car and at first in the blazer, no problems with that and still changed around 3k both oil and filter. Then autozone had a special a while back on valvoline maxlife highmileage semisynthetic and a stp oil filter, so far this is working good no problems. I was thinking of switching to this oil or a full synthetic anyhow so i went with this since it says it is good for vehicles with over 75k miles, which i have. I think as long as you got the right amount of oil in there, that isnt full of crap you should be good to go.

 

On my old 300zx I used only mobil 1 and that lasted me till 225k miles till I traded it in and it still ran great. As a matter of fact I still see it every now and then lol.

On my 2000 Eclipse GT I have tried out a couple of synthetic blends andcoventional oils. With the next oil change I am planning on trying Mobil 1 (only had the car about 6 months)

On my 2000 blazer I tried a couple of synthetic blends and full synthetics including "quaker state suv and truck blend" plus a quaker state full synthetic for trucks, and even a pennzoil full synthetic. But this last oil change I put in the Mobil 1 synthetic and it has been running smoother and overall just has a better drive quality.

No matter what I try I always come back to Mobil 1 it seems. I also change my oil at 3000 miles no matter what. I know that the oil probably can keep going and I know the oil filter can as they are both rated at over 7000 miles (oil filter is at 7000, mobil 1 is closer to 15000 if I am not mistaken?). But I figure that little bit of babying will help keep them running longer.

So my combination for all vehicles always seems to stay at
Mobil 1 fully synthetic 5W30
Fram Xtended guard oil filter (I read up on acouple studies that while this is a pretty expensive filter it has a fantastic filtration rating unlike the standard frams)

 

Those of you that use Mobil 1, have you done a used oil analysis? Some people in various vehicles report high readings of iron in the oil with Mobil 1. Iron can come from the cylinders, rotating shafts, the valve train, and any steel part sharing the oil. It is not an uncommon finding with Mobil 1, but not always present.

 

I had two UOA's done on my Bonneville which got Mobil 1 10w30. One after a 6k OCI, and another after a 10k OCI. Neither had abnormally high wear metals. I don't have either of the UOA's any longer as they went with all of the records for that car when I sold it.

 

I don't think there's a place around here that does UOA's, so... That'd be a no, for me, lol.

 

My mechainc has used Valvoline in all the vehicles i've taken to him so that's what I stick with.
I heard Mobil 1 changed their oil chemistry (from group IV oil to group III oil) recently and isn't considered a true synthetic anymore except in the US. Its still good oil, but prices for M1 seemed to have increaseddespite this "downgrade" soI can't see myself switching to it anytime soon.

 

You can't get any comfirmation from Mobil that they changed the formula, but chemical evidence and word of mouth leads to that conclusion. It's funny that a court ruling allows them to call a Group III oil 'synthetic' (of course, lawyers live on words). So typical in business, drop the quality and up the price.