Join the Car Talk Community!

Discussion Rules

Welcome to the Car Talk Community!

Want to ask a question or join the discussion? Great! Join now.

Sign In Register

0w-20 oil

the owner's manual for my new subaru forester says to use 0w-20 oil, since I have never heard of this, I googled it and found several articles that said this oil improves gas mileage very little but increase engine wear and that car manufactures recommend this oil to help their CAFE numbers and to get you into the show room for a new car sooner. is this accurate?


  • edited April 2011
    I would follow the manufacturer's recommendations. New engines (like the new design in your Forester) are built to work with these oils. Change it at least as frequently as recommended in the manual and you'll be fine.
  • edited April 2011
    In addition to texases' post, I will add that you should get into the habit of checking your oil level on a regular basis. I don't believe that these lighter weight oils are being used to slowly destroy the engine (in fact, the lighter oil flows better through the oil galleys, which are getting smaller with time and different engine designs), but it is true that they help improve fuel economy. Lighter oils also have a tendency to be consumed a little faster by the engine, which means you could end up low on oil if you are the type to never open the hood.
  • edited April 2011
    There's all kinds of stuff flying around the internet & its hard to know whom to trust or the basis for various claims.

    Here is one widely respected website for all things & questions oil:

    I would also just echo the previous comments. I don't find the story plausible. That said, there are often multiple viscosity recommendations that largely depend on air temp. So I have 2 cars where the standard recommendation is 5w-30. But when you look closer it also says 10w-30 is fine if the temps remain above zero. Don't forget to take your own climate into account as you think about this.
  • edited April 2011
    There's really no way to know what actually went into the decision. I know from experience that the tolerances that engines are manuafctured to are far, far tighter than they every were in the past due to a concept called "statistical process control" that manages the processes by controlling variation rather than controlling the parts to within tolerance ranges, and I know that these much tighter engines may need lower base-weight oils to break in properly, but whether that or CAFE requirements drove the engineering decision is tough to guess. I can also tell you that countless hours of reliability testing, qualification testing, and subsequent engineering went into the decision, but have no way of knowing how much it impacted it.

    I seriously doubt the planned obsolescence theory.

    The bottom line is that I believe it's better to simply follow the prescription of the engineers. No good comes from second guessing them. Unless, of course, you is one. (just kidding).
  • edited April 2011
    While there may be some truth to slightly improved mileage, I don't believe that any manufacturer would just plug low viscosity oil into the engine of thousands of cars without thoroughly testing it.
  • edited April 2011
    My car calls for 5W-20 oil. In fact the cylinder deactivation supposedly will not work right if you use a thicker oil, as it works on oil pressure. The engine has very good oil pressure at 58K miles, even when hot, and has not used a drop of oil in the 3,300 miles I've put on it since the last oil change.

    So maybe the thinner oils aren't so bad.
  • edited April 2011
    I am sure you can find someone on the internet who thinks Obama was born in Kenya. You need to treat many things you read on the internet with skepticism, and claims that 0W-20 oil will ruin your engine is one of them.
  • edited April 2011
    I bought a 2011 Toyota Sienna when they came out in March of 2010. It calls for 0W-20 oil. I now have 15,000 miles and the vehicle uses no oil between changes. I have a feeling that 0W-20 oil will become the standard just as 10W-30 was the norm which then gave way to 5W-30.
    I'm certain that Tom McCahill who was the automotive writer for Mechanix Illustrated musgt be rolling over in his grave right now. McCahill didn't like multiviscosity oils--he said that 10W-30 oil was a lousy number 10 and a lousy number 30. He used a straight weight oil one weight higher than specified, took extra time for warm-up and claimed that he never had an engine that burned oil. I've had the same experience--I use a straight 30 weight oil and don't have any oil consumption, but this is on my lawnmower that I have used since 1988. I follow Toyota's recommedations on my Sienna.
  • edited April 2011
    Ya stole my thunder, Mountainbike! Newer cars often have very tight bearing clearances, and the thinner oil can get into the bearings a lot better. Also, certain systems such as variable valve timing setups, in today's engines are dependent on the oil pressure being within a certain range. Using oil that is too thick can interfere with these systems.
  • edited April 2011
    0-20 w oil= sewing machine oil...just how tight can they make bearing clearances? I have been hearing this for the past 10 tight can you go before you get metal to metal contact with rod and main bearings ?

    I have an 89 Mustang GT 5.0 and have been running 20w-50 all year round in Florida and had car since brand new has 208k on it and never touched the engine, runs like it did brand new and never had to add oil between changes.

    These new motor oils are garbage for older cars..I belong to a classic car club and have had many members getting wiped out camshafts using these modern oils. Ford 460's, FE blocks and chevy 327's etc. using newer 10w-30 oils

    I am not saying that these new oils are no good for newer vehicles.

    In my 59 T-bird and 74 Nova run straight 30w all year round.
This discussion has been closed.