A question about motor oils...

03_TrueBlue_GT · Aug 6, 2010

Alright Im wondering would it be wise to use 10w 30 Mobil 1 synthetic oil in my stang during the summer or all the time? Reason I ask is Im using Mobil 1 5w 20 synthetic oil right now and some guys I was talking to at a car show with similar cars said that I should be using 10w30 oil bc of the extreme heat that we have down here in Tx for summers and that the reason 5w20 was used is bc of gas mileage that Ford was trying to get out of these cars... But Im wondering since these newer motors have tighter tolerances and clearences should I just stick to the 5w 20 oil or will 10w30 oil be safe?

Sorry if it was a dumb question but it really troubles me, I want to keep the car in good shape and not have it running hot in the summers down here and want it to last.

Thanks for the help btw!

Gearbanger 101 · Aug 6, 2010

It's true Ford went with the 5W20 to increase EPA ratings. And no...10W30 won't hurt your engine in a high heat environment. Sythetic oil is however designed not to break down under high heat like conventional dino oil is though. Contrary to popular belief, the modular engines weren't designed with any tighter tollerances than the OHV's though. Rune 10W30....5W30....or even the origional 5W20...it all works.

03_TrueBlue_GT · Aug 6, 2010

Oh ok man that helps clear some things up, I didnt want to use a heavier weight oil and restrict it flowing through certian parts of the engine... But I guess I shall be using 10w 30 from now on for summers!

trombonedemon · Aug 6, 2010

Gearbanger 101 said:
It's true Ford went with the 5W20 to increase EPA ratings. And no...10W30 won't hurt your engine in a high heat environment. Sythetic oil is however designed not to break down under high heat like conventional dino oil is though. Contrary to popular belief, the modular engines weren't designed with any tighter tollerances than the OHV's though. Rune 10W30....5W30....or even the origional 5W20...it all works.

I always wanted to know why people thought that the Mod engines have tighter tolerances. Wouldn' looser tolerances make a lot of engine noise and vibrations, so why would Ford build any engine like that. What does "tighter tolerances" mean.

Dark04GT · Aug 6, 2010

03_TrueBlue_GT said:
Alright Im wondering would it be wise to use 10w 30 Mobil 1 synthetic oil in my stang during the summer or all the time? Reason I ask is Im using Mobil 1 5w 20 synthetic oil right now and some guys I was talking to at a car show with similar cars said that I should be using 10w30 oil bc of the extreme heat that we have down here in Tx for summers and that the reason 5w20 was used is bc of gas mileage that Ford was trying to get out of these cars... But Im wondering since these newer motors have tighter tolerances and clearences should I just stick to the 5w 20 oil or will 10w30 oil be safe?

Sorry if it was a dumb question but it really troubles me, I want to keep the car in good shape and not have it running hot in the summers down here and want it to last.

Thanks for the help btw!

5w20 works just fine in our cars.

Many people will say to use heavier oil but it really isn't necessary. It is nearly impossible to test if a certain oil will make the engine last longer because everyone drives different. (in real world driving, of course you could test it in the lab)

You don't have to change your oil for the summer, the hot air does not change how your engine handles oil.... this is because your engine always operates at the same temp no matter the temp outside. What really makes a difference is the oil in cooler climates. You need to make sure you are running that lighter oil if outside it gets into the subzero temperatures - for those subzero startups. I doubt that is a problem in houston. Other than that, run 5w20 and enjoy what the engine was designed for.

Gearbanger 101 · Aug 6, 2010

trombonedemon said:
I always wanted to know why people thought that the Mod engines have tighter tolerances. Wouldn' looser tolerances make a lot of engine noise and vibrations, so why would Ford build any engine like that. What does "tighter tolerances" mean.

Engine tolerance (or clearance) between components of the OHC and OHV engines are virtually identical. Looser clearances in say an area like pistons/piston rings can often allow an engine to rev out much smoother and easier and allow you to sustain high RPM operation more safely. The downside being a slight loss in compression and some blow by. It’s not uncommon to hear a little noise on cold start up and for the engine to use a little more oil between changes.

Get things too loose and they'll rattle and wear more quickly (main/rod bearings). Tighter is quieter, and smoother for general operation, but too tight can also limit the amount of oil in the immediate area and increases chance of contact on cold start up, or high RPM operations...which could cause abnormal wear to components and in worst cases all out seizure.

twogts4us · Aug 6, 2010

Also realize that the oil pump in these mod motors is not made to run heavy oil...and they are not the strongest engineering design to begin with.

Gearbanger 101 · Aug 6, 2010

twogts4us said:
Also realize that the oil pump in these mod motors is not made to run heavy oil...and they are not the strongest engineering design to begin with.

The pumps aren't bad until you run into heavy detonation. That's when the powdered oil pump gears tend to go south. Not a perfect design, but no worse than twisting off the oil pump shaft in a stock OHV set up. In any case, I've seen 600hp cars running the stock pump with no issues.

I've got the FRPP high volume pump on my 4.6L. It was probably unnecessary, but I kinda overbuilt everthing on the car. The result is lots of pressure on the dummy gauge and probably a 5-7hp loss in the higher ranges because of the power required to drive the thing.

streethorse · Aug 6, 2010

Gearbanger 101 said:
It's true Ford went with the 5W20 to increase EPA ratings. And no...10W30 won't hurt your engine in a high heat environment. Sythetic oil is however designed not to break down under high heat like conventional dino oil is though. Contrary to popular belief, the modular engines weren't designed with any tighter tollerances than the OHV's though. Rune 10W30....5W30....or even the origional 5W20...it all works.

I agree, they all will work. Ive even gone to the extreame of running
Mobil 1- 20w/50 in the summer, left it in for 4k, no problem at all.
Sure, in a colder climate its 5w/20 year round. Its 105* here right now...

Dark04GT · Aug 6, 2010

streethorse said:
I agree, they all will work. Ive even gone to the extreame of running
Mobil 1- 20w/50 in the summer, left it in for 4k, no problem at all.
Sure, in a colder climate its 5w/20 year round. Its 105* here right now...

20w50. => 5w20

streethorse · Aug 6, 2010

Dark04GT said:
20w50. => 5w20

Hey, I tried it as experiment... it works... but I run 5w30 now...

trinity_gt · Aug 6, 2010

I put 5W40 synth in my little turbo GTI and will be changing to that oil for the MGT next change.

Ford recommends 5W50 for the "GT" and I believe for the GT500 as well. I think there's far more latitude for oils on these engines than some believe. 5W20 is not about clearances, it's about reducing pumping losses and getting another 0.5MPG. If Ford is using heavier weights in their "performance" modulars then I'm okay doing the same with mine

bdcardinal · Aug 6, 2010

Ford says 5W50 in the GT Supercar and 2007+ GT-500. Also in the mod motors in other countries that are built on the same line as the ones used here take 10W30 and 5W40. Look up the maintainence for the BOSS 290, or 315 motors in the Australian Falcons you arent gonna see 5W20 on those mod motors.

BannonJr · Aug 7, 2010

I ran Amsoil's 10w30 ATM this round and got back an amazing report from the lab.
Thumbs up for the ATM!

A question about motor oils...

03_TrueBlue_GT

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