Oil Viscosity and Consumption

toyota

#1

A couple of years ago, the Toyota dealer switched my '03 4-cylinder Camry from 10W-30 to 5W-20 oil. This was done following a tech bulletin from the factory stating that the lighter oil was approved for the 2AZ-FE engine, and (in theory at least) could improve fuel consumption. Looking back, it seems that at about exactly the same time, my oil consumption went from a quart every 4000 miles or so to about twice that. I mentioned it to the service manager at my next visit, and he said that there was no way that the change in oil could have lead to increased consumption and that a leaky valve cover gasket was the cause. As they wanted about 500 bucks to change the gasket, I held off on the basis that I could buy a lot of oil for $500.



Well, the oil consumption gradually worsened until I was going through a quart every 1000 miles or so. Although I could see no evidence of drips under the car, I decided that it was time to bite the bullet and have the gasket replaced. This was done at the last service (and they agreed to do it for considerably fewer $$ than the initial quote).



Well, it’s now been about 1300 miles, and I’ve gone through nearly a quart of oil. It seems that replacing the gasket helped some, but there’s still another root cause for the oil loss. The car has just over 80,000 miles on it, so some oil consumption is to be expected, but I’m tempted to switch back to the 10W-30 to see if it makes any difference. My question: Is there any reason to think that a switch from 5W-20 back to 10W-30 might improve things? By the way, the fuel savings from the lighter oil have been virtually unnoticeable.


#2

Me, I’d change back and see if it makes a difference. Absolutely no risk, see what happens.


#3

I agree. I have never liked the idea of increasing fuel economy by lowering the viscosity of oil. At some point…you will increase wear of the engine in some circumstances.


#4

I don’t remember why Toyota changed the recommendation but they did and it was not just for better mileage. Also note that a quart in 1,000 miles is not considered bad for most cars. It seem high to me, but the industry seems to differ.

In real life I would not expect much difference.


#5

The lower first number means that it flows easier at lower temps and you get less wear at start up. If it is burning oil, then you could switch to 5w_30 and get the lower temp protection and the higher temp viscosity to keep it from flowing past the rings.


#6

I “third” the vote. And I agree with Missileman’s comments.

I’d also change the PCV valve if it has one (my '91 Camry did not). A clogged PCV valve can allow excess pressure to build in the crankcase and thus under the valvecover and cause seepage.


#7

You hit on an important point. My Toyota also got the bulletin that I could switch to 5W20 or 0W20 synthetic. Same story; the real story is CAFE mileage conpliance. Most new Toyotas now specify 5W20 or 0W20 synthetic, but in the Matrix I rented recently, the manual now says that oil consumption of 1 quart per 600 miles is “acceptable”!!!

In other words, fast highway driving or pulling loads with the 20 grade oil will cause higher oil consumption. Your dealer is blowing hot air. And Toyota is talking out of both corners of its mouth.

My son bought a 2004 Mazda 3, which also specified the CAFE driven 5W20. I advised him to put 0W30 Mobil 1 synthetic in to avoid the high speed oil comsumption. Now at 90,000+ miles the engine runs perfectly and does not use any significant amount of oil.

A friend of mine who is an oil consultant, coached a Corvette team to victory by using 0W20 synthetic. It made a difference in horspower, but oil consumption was way up. In a 500 mile race that’s no big deal. But there was no doubt also increased engine wear.

I would stop going to the dealer and use 5W30 dino or 0W30 synthetic from now on. Your oil consumption will decrease, unless you have already caused excessive wear from using the 20 grade oil.


#8

I really doubt that 10W-30 was recommended in the manual for your Camry, more likely 5W-30.
Get the whole PCV system checked out, not just the valve, the tubing to the valve could also be clogged.
I would go back to 5W-30.


#9

I noticed the same thing first on my motorcycle. 10W-30 is recommended and it historically burns almost no oil. I switched to 5W-30 synthetic because lots of people recommended it to reduce gear clash and promote smoother clutch operation. Mission accomplished.

No too long after that, I started to get lifter noise on exit from high speed driving. Checked oil and Whoa! way low. Topped off and same kind of consumption rate going forward. Switched back to conventional 10W-30 and it’s back to normal.

Fast forward two years and I go back to the same synthetic formulation and lo and behold, it’s consuming oil again at a fast clip. Back to the original oil and guess what? Virtually no oil consumption.

A bike is a harsh environment for oil. So I tried an experiment on one of my caged vehicles. Similar results.


#10

I tend to agree that it’s a CAFE issue. Manufacturers are trading off the life of the engines to comply with ever-tightening regulations. And it’s going to get worse.

Your comment about racing engines running thin oil was a good one. and, as you pointed out, the race teams don’t have to worry about excessive oil consumption or long term wear. Power and speed are their only goals, and anything legal goes.


#11

Yes, you’re right. I should have said 5W-30. Thanks.


#12

My car is at the neighborhood Exxon station right now for a change back to 5W-30. I will report on the results in a month or so.