I bought my 2010 HHR LS with 80,000 miles, and my mileage is now 120,000 miles. I’ve always used regular oil, not high mileage, with no leaks nor added oil between changes. I’m now wondering if I should change to a synthetic or semi synthetic oil since my mileage is increasing. I plan to drive my HHR forever or thereabouts.

Thanks for any help.

 

You should change to an oil that has the Dexos label. They could be either syn or semi-syn.

It even says so on your oil fill cap.

Never use "high mileage" oil !!!

 

You’ve been using the wrong oil, Dexos 5W30 is what the owners manual says

 

I would stick to regular oil as you have been to this point. But a 5w-30 Dexos approved oil.

Adding synthetic now will clean the inside of the engine & could well cause oil leaks.

And as Don said: NEVER use High mileage oil..

 

This has already been discussed a lot, and all this is true, but if you will, here are my 5 cents in addition.
Dexos 1 is a standard that is still common on the market. Designed for gasoline engines.
Dexos 2 - more modern. Intended for gasoline and diesel engines of cars, incl. turbocharged and variable valve timing.
In your case, you can use both standards painlessly. By the way, I am doing the same.
That dexos is a certification of oil for GM you know without reminders. I can add that "dexos" certification is a very desirable condition, but not critical. There were times when I used "non dexos", and this did not affect the health of the car. Speaking in detail, these were synthetic oils with certification of SN according to API standard. What for? Mainly due to savings, by a lucky chance, high-quality oils with a good discount caught my eye. Hand on heart, the dexos standard is more beneficial to the GM itself than to the users. Just a way to make a profit on this side. I plunged into the problem twice in different years and did not see a big difference between the characteristics of “dexos” and “not dexos”. Within the margin of error. Who wants to, can repeat my research.
About 5-W30: keep holy. This is not in doubt.
Synthetics or semi-synthetics: I highly recommend synthetics as this oil during operation changes its properties little (you know, the oil contains a bunch of additives, catalysts, stabilizers and other chemicals).
High mileage oils: guys are telling the truth. The more often you change the oil, the healthier your engine. The oil resource is reduced: city traffic at least 35% of the total mileage; engine stops and starts - the more, the less resource; "non-laboratory" air temperatures (cold winter or even just winter, hot summer); aggressive riding with sharp accelerations and sharp braking. If there is at least 2 points from the listed ones - the manufacturer’s promises are divided by 2. Read 10,000 miles on the bottle - a real replacement in 5,000.

 

I switched to full synthetic on both my HHR and GMC Sierra at around 100k miles each. I already had a small leak on my HHR already when I switched, it didn't get worse and now at 162k the leak stopped. Most likely due to dirt build up at the spot of the leak. My Sierra runs quieter now too. It now has 157k.

I use a store brand Dexos approved full synthetic. It's not much more expensive than conventional oil.

Probably not so much on these engines. However using Dexos is critical is on the newer small displacement turbo charged engines. The spec for it includes remediation for LSPI (low speed pre-ignition). My wife's Buick Encore falls under this.

 

This is the holy truth