i was using pennzoil high mileage 10w40 and i just switched yesterday to regular 10w30. high mileage was $45 and regular was $25. im a college student now so i gotta nickel and dime everything

 

Holy crap...

Where are you buying your oil at? Wal-Mart just had "Q" synthetic oil on sale for $18 for a 5 qt jug. (Quaker state)

 

Becarful of Wal-Mart. Make sure that you dont end up getting use oil like I did.

As to the OP I think it does not matter what kind of oil you use so long if you change it on a regular. Oil for a car only job is add luster to the engine from wear and tear when the piston are running. But i personaly use to use Royal Purple synthetic but I am turning back to Mobil 1 because the price has jump dramaticly. So what I am going to do is run Mobil 1 for 3k and after that contune to change it between 4-5k.

BTW to anyone with a Costco card, check the coupon book there is a deal on Mobil 1 5-30w and 10-30w for $10 dollar off. That is equal to $25 for a case of 6 qt total. Limit 3.

 

Walmart near me blew out their Pennzoil full synthetic 5qt jugs for $10.00 each! Bought all of them. Had to roll around 2 shopping carts. Hold the flames. I do an oil change every 6 weeks.

 

I don't see how common sense would say going from synthetic to conventional would harm the engine. First of all, an engine doesn't really need synthetic, just a good grade conventional oil, change at regular 3000-4000K intervals (slight overkill, but what the heck right?). So, if you go synthetic which is even better lubrication, then how does going back to what it can take be bad?

I believe the reverse would be bad, going from conventional (with high mileage already) to synthetic could cause leaking as the synthetic flows better and might seep out of areas that the conventional was not.

 

going from conventional to synthetic is not a problem so long as there are no sludge buildups at any of the cam seals / crank seals... here, the only potential problem is that the additional cleaning agents of the synthetic oil would attack a sludge buildup and, a leak that was minor might now be major...

if the engine was 100% dry with conventional, it will be dry with synthetic though...

 

Wow, you must put a lot of miles on that car. Otherwise, it's wasteful... just my opinion.