Oil change

The standard size drain plug is 15mm or 17mm.

The issue of switching to a different oil isn't so much synthetic to regular. It's more of switching from one oil to a different one, meaning brand. Any oil you buy today for gas engines will more than meet the requirements of an engine built five years ago, but it's the additives that may not be compatible. Those are corrosion inhibitors, detergents, seal conditioners, and viscosity index improvers.

While all of those additives might work fine on their own, one of them in your new oil might attack an additive from the old oil. The good news is most additives wear out in about 3,000 miles. Also, you're draining most of what's left out during the oil change. If you pick an oil you like and stick with it, there's little chance you're going to have a problem.

I AM aware of a few people who switched TO synthetic oil, then developed oil leaks that got progressively worse. In all cases, those leaks dried up almost completely after they switched back to regular oil. I don't have a good answer for that other than I saw the results.

This was an experiment on an engine I thought was about to fail, and was done to show my students what some engines are capable of. After five years of this abuse, it became obvious there was no point in changing what was working. I am not suggesting anyone else do this, especially when newer engines wouldn't survive, and I don't do this to any of my other vehicles.

To explain further, I have to add a quart every 1,000 miles, so the engine gets continually replenished with the additives in the oil. There's enough additives in one quart of oil to do what it needs to do, so my engine gets new additives every 1,000 miles. When you go 3,000 miles or more, your additives are depleted. Mine never are. Plus, I use only the cheapest farm and home store oil I can find.

That argument doesn't make up for the sludge and carbon that build up in the oil, but replacing the filter every few years makes me feel less neglectful. The point of this reply is to show that you can have a grossly-neglected engine last for 420,000 miles, and you can have a carefully-maintained engine fail in well under 50,000 miles.

My former student who works at a Ford dealership as an alignment and engine specialist tells me the horror stories when he calls me every few days. To listen to him, you better stick with the highest quality oil you can find.