Considering oil grade switch.. need help
 

I have been running 10w30 in my car for the past 3 years. I have heard switching to a lighter weight such as the 5w20 may boost FE. My main concern is if my engine can handle it or not. It's a 2.0 mazda 4 cyl with close to 136k miles, always used conventional oil. I considered switching to synthetic as well but I have heard horror stories about loosening sludge and killing the engine. What do you guys think? Thanks in advance.

Roger

I know that the "Zetec 2.0" in the focus is the same as the Mazda 2.0 and I believe they haven't changed that engine since the early 90's.

I'd go to a 0W30, youve got a few miles there and a 20 might be too thin for an engine with some slop in it.

Since you live in Louisiana and don't need to worry about winter I would just keep the 10w30. You're not going to see that big improvement in FE with the lighter oil.

Duffman, I think I'm gonna go with your suggestion. I just looked into Amsoil, they have a lot of data supporting their oil. The 0W30 apparently is used in Police Fleet vehicles and is warrantied for 1 yr or 35k miles :eek:

Warhawk626
The "correct" oil depends on the clearance between the bearing shells and the crankshaft, connecting rods, camshaft. A less viscous oil may escape out from between the bearing shell and crank-etc. faster than the oil pump can replenish it.
I would suggest you get a real, mechanical, oil pressure gauge to at least compare what sort of pressures you are getting now, and after the lighter oil. The later versions of your engine may have smaller clearances in the bearings than yours does.

Guys, it's mostly Ford and Honda that spec 0/5W-20 oils ... and I don't think they redesigned a single engine with this thinner oil in mind. All the engines that call for it are older designs with the same clearances as when they called for 5W-30 (like Dad's Mercury Grand Marquis with its 4.6L V8).

I've seen dozens of UOAs (Lab tests) using 5W-20 and they usually look superb. I'd use 0/5W-20 without much reservation. Just don't go over 5,000 miles without doing a UOA from a place like this:

http://www.blackstone-labs.com/gas_engines.html

If you have been changing your oil like you should I'd go right to synthetic and not look back. Be honest, have you been a good boy? If not I'd use the high mileage blend that valvoline makes in a 5-30. If no leaks after a few thousand miles you could get away with a synthetic or a 5w-20 motorcraft blend. Like the above poster said you should get a reliable oil pressure gauge and at least go to the 5-30 of the same oil you have been using and see what the gauge tells you. To make this even more complicated, some 10w-30s end up being "thinner" after use than a 5w-30.

i run 5w30 in a 350

I'd try it. I'm running Motorcraft 5w20 in our Aspire that has a Mazda designed 1.3L. It loves that particular oil. If you taken care of it I wouldn't worry about killing it the Aspire has 208k on it. With all the changes I can't say for certain but I think it gave me about a 2 mpg increase.

Let us assume you are correct. Why then were these engines specd with 10w-30 to begin with if the bearing clearances are unchanged? I can tell you why the spec was changed to 5w-30: To improve fleet fuel economy to meet govt. standards. As long as the engine outlasts the warranty, it is not the manufacturers problem.

If fuel economy is your aim, I wouldn't run a high-mileage motor oil in your engine as they are formulated to be a tad thicker than other oils in the same grade. They lack the API "starburst" energy-saving symbol on the bottle for a reason.

ttoyoda, I'm not sure they all were? The 4.6L was originally spec'd to use 10W-30? That may be ... but my Dad has had a few of these and all I can remember was buying 5W-30 for his ... until the switch to 5W-20.

It could be that 10W-30 was the "in" oil at the time the engine hit the market. Most engines were spec'd for 10W-40 several years before 10W-30 and 5W-30 is still the most common weight. I'm not sure the auto companies agonized over these recommendations. The oil worked well enough ... and the EPA was pleased to see thinner and thinner oils being used to improve economy among the non-thinking mob of North American motorists.

(Most of us that read UOAs have seen 10W-30 shear down almost as fast as 5W-30 nowadays)

When 5W-20s first hit the market, they were LOADED with extra barrier anti-wear additives like boron and moly. Many still are. So, having the best additive package may have contributed to excellent UOAs ... despite the fact the engines were designed during the 5/10W-30 era.

I should add, to be exact, that 5w-30 oil is allowed in my 1992 toyota motors when the air temperature is BELOW 50 F. I do 5-30 from december to march usually. A long time ago, I forgot to change to 10-30 in one of my cars, but was reminded to do so because when the weather got hot, the motor was much noiser, it had a nasty sort of clatter. Putting 10-30 in made it quiet again.

Bror Jace -

I just did that test and my car came out squeaky clean. I am running a heavier 10W40 oil, though, because I am at 155K+ miles (Saturn S-Series like to burn oil). I may go back to 5W30 in my next oil change, and check the dipstick a little more often.

Just to oil the waters a bit more, here is another great website on engine oil :

Bob Is The Oil Guy (BITOG)
http://www.bobistheoilguy.com/

CarloSW2

Pfft, typical Ford!

FWIW, I've switched over two Chevy four bangers to full synthetic after running an engine flush. One engine I switched at 70Kmi, the other at 88Kmi. Both engines are still in service today with zero ill effects. I would also advise you to stay away from high mileage formulas.

I back up synthetic.