CarTalk.com Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Oil weight

I have a 1992 Chrysler Concord with about 85,000 miles on it. The manufacturer recommends 5W30 oil. My husband says that 10W40 would be better for the engine, and wants to put that in instead. Is this a good idea or not?

I would stick with the recommended oil. Why does you husband want to change to the heavier oil?

2002, Eh ? Stick With The 5w30.
Are You Trying To Find Something Nice To Do For It ? Use A Fully Synthetic Oil, Like Mobil-1 5w30 Full-Synthetic. Keep The Oil Changes On Schedule To Keep Clean Oil In It.

CSA

What, exactly, does your husband think will be better?

I had a bad experience with 10W-40 oil in my 1978 Oldsmobile. The manual said that either 10W-30 or 10W-40 could be used. I reasoned that the higher viscosity was better, so that is what I used. I found out that certain brands of 10W-40 had polymers to increase the viscosity that also caused carbon build-up on the pistons. I had to run Casite motor tune-up through the engine about every 90 days to keep the engine from pinging. When I switched to 10W-30, I no longer had the problem.
Your Chrysler has fuel injection and the engine runs cleaner than my 1978 Oldsmobile. Therefore, carbon buildup probably would not be a problem. However, the 5W-30 provides better lubrication when you start the engine where most bearing and cylinder wear occurs. Stay with the 5W-30. It will give the best protection for the engine.

If you have the 2.7l engine, you better stick with the 5w30. This engine has a timing chain with a tensioner that uses oil pressure. If anything causes that tensioner to stick, the engine will be ruined immediately.

Stick with the 5W30, as mentioned. Using 10W40 in an area with cold mornings will increase engine wear on startup. Your husband must believe that more is better, although I’ve seen this oil used in TROPICAL countries where the outside temperature over night stays right up to 75F. Hawaii and South Florida are the only areas where this 10W40 can be used withour causing excesive engine wear and other lubricating problems.

So, unless you live in those areas, stick to 5W30.

Use the recommended oil. You will get better mileage and better oil flow in all weather. The only reason to go to thicker oil, is if you are losing oil past the piston rings. The thicker oil will not pass the ring as easily and you will not need to add oil as much.

If you still have the owner’s manual, chack the oil requirements. They are often given with temperature bands. If you live in a warm climate, 10W40 might be OK. In any case, do what Chrysler recommends and only modify if Chrysler says it is OK for your climate.

I don’t think the 10w40 will hurt anything on your engine if your husband feels better using it. I use 10w40 in all 7 of my cars year around (temperatures from -5 to105* F), they are spec 5w30 and 5w20. One of my cars has over 517K miles on the original engine without any rebuilds. 4 of the others are over 100K miles, with 2 of them being near 200K and use less than a quart of oil every 5K miles.

FordMan, how many of those 7 vehicles have a hydraulic timing chain tensioner or variable valve timing?

1 @ 179K+ miles, uses usually less than a quart of oil every 5K miles.

Keith made a good point. Modern engines use their oil for purposes other than just lubrication. In many modern engines they’re used as a hudraulic fluid to do things like operate variable valves systems and, apparently, operating a tensioner. Using other than the recommended oil in modern engines carries risks of fouling up one of these systems.

Use the recommended lubricant. Assume the engineers at Chrysler knew what they were doing.

I recommend using the recommend fluids. While Lots of people will have personal examples where using something else worked well and some will have experiences where using the recommended fluids worked well.

The problem is that most of those who want to ignore the manufacture’s recommendation likely is basing their recommendation on results grandpa had with a car fifteen years older than today’s cars. The manufacturers have been closely checking the results of different oils in the cars they are going to sell. Unless you buy a number of cars as test cars and drive them the equivelant of say 20 years I would suggest the manufacturer knows best.