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What have I done?

At my last oil change I asked for their “best” service.

So my 2005 Deville with 39,000 miles that has always used Pennzoil 5W30 is now using Castrol Synthetic!

How much trouble am I in??


You’re in no trouble whatsoever.

thank you…do I stay with the synthetic?

You can stay with synthetic oil longer than with conventional.Or switch back.But you are in no trouble.

Some people talk bad about Pennzoil and Quaker State oil. So, with the car costing so much to buy; why not at least stay with synthetic oil? The regular Castrol is supposed to be good stuff too. Valvoline and Havoline have good reputations. I can’t tell the difference and I used to use Pennzoil. The only engine I lost was from failure to keep oil in a leaking engine.

thanks for the comments!

All you’ve done is pay a little more than you had to. The synthetic oil will not hurt your car, and you can switch back to regular oil next time if you choose.

Brand name means little, if anything.

As long as the same 5W30 weight is used, you have nothing to worry about. If you live in a very hot or very cold araa, it will make your engine last a lot longer.

There is no problem. You can freely switch back and forth between regular and synthetic. There may be a very slight advantage to synthetic. Find something else to worry about.

From my personal experience…Synthetic oil IS better then regular dyno (at least the Dyno I was using 15+ years ago).

No matter what oil I used I’ve been able to keep the engines running STRONG past the 300k mile mark. The vehicles I used regular Dyno on were still running strong at 300k, but burning a little oil (about 1/2 quart every 3k miles). The vehicles I’ve used mainly Synthetic oil on were NOT burning 1 drop of oil between oil changes (every 4-5k miles). I also noticed I have a easier time starting my vehicles when temps get near or below 0.

Actually, the OP paid a lot more for synthetic.

cat, I’d switch back to the non-synthetic blend when you change the oil next, unless you want to extend the time between oil changes. I’d use non-synthetic and change the oil when the ‘change oil’ light comes on when you start up the car. When it first comes on you have less than 10% oil life left.