I got an oilchange and I think they trashed my car it was running fine but as soon as I left pepboys it started overheating turns out they didn't put oil in my car and I drove a ways didn't develop a knock tho luckily but it keeps overheating really bad im gonna try n replace the thermostat today because it doesn't overheat at night when it's near freezing the needle will shoot up to a cm under the redzone and fluctuate over the normal temperature but this morning when it was 36 degrees it ran normal... Any ideas besides replacing the thermostat which im gonna do at 3 today once it arrives at autozone

Does the starter seem to turn the engine over the same as it once did?

I would see how the starter spins the engine with the plugs removed. How does it turn by hand, using a wrench?

At this time, you could do a compression check.

I would suspect damage to the bearings or other internal engine parts, causing extra friction.

As for the thermostat, I would remove it and test it in on the stove. Put it in a pot of water and see if it opens when it should - i.e. before the water boils.

This is quicker and cheaper than installing a new one.

Have you spoken to Pep Boys about this? If you can prove there was no oil put in then they will most likely cover the cost of repairs. As everyone else has said there may be damage to your engine and that damage may be causing increased friction and the friction causes heat. Low outside temps may mask these effects put they will only get worse. If internal bearing clearances get too high due to wear then the oil wedge which protects journal type bearings will be in effective and something will break.

Wow. That's terrible service. They could have harmed your engine. Volvo engines are tough, but If they did cause damage because of negligence, you could take them to small claims court (no lawyer needed) and probably win, if you can get a mechanic to sign a notarized statement as to the cause of the damage. That and your Pepboys receipt for the oil change would convince a judge to rule in your favor. Collecting the award would be up to you though.

When you left Pepboys, did your oil pressure warning light in the instrument cluster come on?

If so, how far did you drive when it was on? How fast?

When you put some oil in, did the light go out?

Is there smoke in the exhaust now, or abnormal engine noise?

No smoke the only reason I noticed was cy they said make sure to see if it overheats... Im replacing the fanclutch tomorrow and possibly it's just that... There's no knocking or smoke the car just shakes when I start it now