Fess up, who is running 20wt in a 30wt motor?

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Nov 10, 2003
So Cal
Who here is running say Mobil 1 0w-20 in a motor that calls for a 10w-30?

What motor/vehicle do you have, for how long have you been running it, and what are your impressions: Both factual(UOA) and subjective(more/less noise, better throttle response and mpg, ect..)

Now don't be shy, I KNOW you're out there


Originally posted by Darryl:
Who here is running say Mobil 1 0w-20 in a motor that calls for a 10w-30?

Oh PLEASE...they're ENGINES, not motors.

Have you been listening to too many NASCAR drivers?...you know the ones--the guys who talk about the car 'peenching'.
Ummm...Ok.... Not exactly what I was looking for.

And it's funny you should mention it, because I DO make my living from NASCAR

Anybody else?

Theyre was a UOA posted from Buster with 0w-20 in his Toyota Corolla that specs 5w-30 I'm sure. Results were pretty much identical to his other UOA with various other brands and viscosity grades.
I did it for 300 miles as a low viscosity flush.

Nissan Frontier KA24DE I4.

I did not care enough to do a UOA. My impressions were that vavetrain/timing chain noise was up quite a bit but throttle response was better. I did not monitor fuel economy.

I was concerned about bearing wear after reading TooSlicks thread. Considering the oil I normally run I have no plans to repeat this.

If your engine doesn't call for it the only use I can see for it is as a flush.


Oh PLEASE...they're ENGINES, not motors.

Have you been listening to too many NASCAR drivers?...you know the ones--the guys who talk about the car 'peenching'.

Motor (from Dictionary.com):
1. Something, such as a machine or an engine, that produces or imparts motion.
2. A device that converts any form of energy into mechanical energy, especially an internal-combustion engine or an arrangement of coils and magnets that converts electric current into mechanical power.

I do prefer the term "engine" too though!

I agree with GSV. There was a lot of engineering done to determine whether a certain grade of oil will work on a particular engine. I wouldn't bother straying off spec for the little bit of fuel economy gain you'll get.

[ January 16, 2004, 07:47 PM: Message edited by: rpn453 ]
I guess Ford Motor Company has it all wrong from the start right along with the Chilton Motor Manuals. Next we will have to say torque pounds feet instead of foot pounds of torque.
I ran this experiment twice with synthetic 5w-20 and 0w-20 grades. The results were extremely repeatable and bearing wear was 5-6 times what I see with the Amsoil 0w-30 or 5w-30. The Amsoil 5w-20 has a HT/HS of 2.9 Cp, which meets the min spec for xw-30 grades. I knew that going in and was very surprised with these results.

Thin oils and low rpm, high load, engines are a bad combination. I drive my Tacoma at 2000-2500 rpms most of the time, due to the gearing (3000 rpms is 80 mph) ....You can run the Synergyn 0w-20 in a Honda S2000 and get low bearing wear (yes, I know they recommend 10w-30), but I wouldn't try it in low rpm truck engines.
My "motor"
is in the form of a pushrod, low rpm, Dodge Dakota. It redlines at 4800rpm and stays between 1800-3000rpm's for most of the time.

The reason I'm asking this is because I did the same type of "flush" with Castrol GTX 5w-20 for 200 miles. Throttle response was alot better than the Royal Purple 10w-30 I had been using.

I now however, have settled on Mobil 1 0w-30 and it seems real close in terms of "feel"(E N G I N E
response) to the 5w-20. I plan on staying with the M1 0w-30 for the long term.


[ January 16, 2004, 08:41 PM: Message edited by: Darryl ]
Does using 5w20 in an application approved by TSB where 5w30 was the original recommended fill count?

I use 5w20 in my '99 F150 with 4.6l V8 which originally specified 5w30. I switched around 85,000 miles.

Observations are:

No change in consumption, if anything has improved. 1 qt every 4-5000 miles.

Fuel mileage difference was slight, but 5w20 did get around .2 mpg better (not nearly enough data to call this a trend though).

Cold start performance seems better, started to -18F this winter with no problems.

Slight feel of more peppiness, could all be in my head.

UOA's show better wear than the previously used 5w30 and have allwed a major extension of oil change intervals...
Tooslick, I was thinking about your testing. I was that it was lack of hydrdynamic protect due to viscosity gradient.

Tonight I thought it might also be a problem with hemorageing of lube at the pump. Just becaue the pressure was good enough not to trip the oil pressure light does not mean it was not lower. We also do not know what the volume was at the bearing. It could have been hemerageing at the bearings intermitently. Most oil guages have a buffer to prevent wild swings in readings.

Just some random thoughts though!

[ January 17, 2004, 02:42 AM: Message edited by: JohnBrowning ]

Originally posted by TooSlick:
Thin oils and low rpm, high load, engines are a bad combination. I drive my Tacoma at 2000-2500 rpms most of the time, due to the gearing (3000 rpms is 80 mph)

I undertand your reasoning, but what about Ford retroactively recommending 5w20 for older 4.6 V8s? These engines in most applications rarely see much over 2500 rpm, and with Ford's notoriously poor TCM programming are prone to lugging due to delayed or nonexistent downshifts from 4OD. (And from what I've seen, this problem still exists in 2003 and 2004 models.)

Also, we have to consider the big V10s in Ford trucks. These could hardly be considered hi-rpm engines, and I would guess that no matter what the gearing, these engines will spend most of their time under 2500 rpm.

My guess is that any small to medium size V6 or V8 engine that was originally spec'd to run on 5w30 can safely use 5w20.

Interesting that the 5W-20 performed markedly better for you. Were they both dino oils? If so, I'm thinking the generally higher quality of the 5W-20s (ie more Grp III stocks, more demanding tests) might account for that as much or more than the viscosity?
Yes, both all of my UOA results are on dino oils.

That being said, on my F150's the previous dino was mostly a group II/group III blend also (a "synthetic" blend), with similar detergent packages (on the basis on UOA).

Is the quality of the base oil required or not? On the basis above, it doesn't appear to be the case.

I was wondering if anyone else would pick up on the Ford modular V8's and the V10 also using 5w20. In my F150, I pull maybe 1500 rpms @ 55mph and pull 2000 rpms at 70 mph. Not exactly a high reving application, and the motor doesn't see much time over 3000 rpms.

I will grant these applications are more rev-happy than V8's of old, but i wouldn't broad brush things saying that a 5w20 can' survive a low reving application, where they are clearly doing well in the Ford pickups.
I tried M1 0-20 in my Mazda Miata in an attempt to get more power and fuel economy. My results were poor, as the fuel economy went down as did the output. My reasoning for this was that the engine is 10 years old and 100K+. The thin oil does not seal the rings as well and the result is more blowby.

BTW, the oil only made it 2500 miles before I lost oil pressure. I never sent it out for UOA, however the sample container with the used oil in it has about 1/4 inch of sediment in the bottom!

This engine has had M1 since day one, and a recent timing belt change (prior to 0-20) showed no deposits of any sort in the valve train area.

My suggestion is not to use 0-20 oil in older engines, as it is unable to maintain safe oil pressure after a few miles.

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