Larz is going to Mobil 1. I have ran 10w-30 as long as I've owned my FD. Is there a preffered different viscosity for synthetic? Can or should I run 15-50 in a street driven car with no adverse effects or better yet some good ones? Is 15-50 too thick for street use?

 

I run 10w30 synth most of the time. Only in the dead of summer when it is really hot out here in Phoenix do I go up to 20w50 or 15w40. Last summer actually I think I stayed with 10w30 through all the heat. I dont think it matters so much when you run synthetic, just dont go too thick in the winter would be the only thing to worry about.

 

I use the heavier 15w-50, because of fuel dilution and Florida weather.

 

IMO, 50 weights are too heavy for the street. You'll really never heat up the oil enough just driving on the street to take advantage of the heavier weight, and all you'll do is end up working your car harder trying to push that stuff through the engine.

If you ever plan to track the car, I would recommend using the 50 weights on the track at that time but I would stick to 10w30 on the street (I do and I see temps in the 100's with high humidity as well).

 

10w-30 it is. Thanks guys.

 

I also run 10w-30 mobil 1 in my car all the time.

 

i know some people say that you should not go synthetic...why? Is there any benefits of having synthetic over regular or vise versa?

 

search for it, there are TONS of threads.

 

The thing that got me was a guy claiming his temps went down during daily driving. Anything that lowers the heat of the rotary beast is a good thing.

 

I'm the guy. Or one of them. I have been using Mobil1 15/50 for a few years. It doesn't get too cold here in the winter, or I would might use a lighter weight. Honestly, I don't think the weight matters very much.

 

as others have said, the apparent viscosity never stays 50 weight for long in these cars with 10% fuel dilution

 

With due respect for Mahjik... ^that's also one of the reasons I've stayed with Mobile 1 15-50.
I'm not sure it's 10%, but I do suffer from significant fuel dilution. I don't have any numbers, but anecdotally it seems to maintain oil pressure better over the time between changes. While the car isn't tracked, I don't drive it in the winter, I'm careful about warming it up before getting into boost and change about every 2.5k miles.

 

Yes, but you'll also notice the increased oil pressure due to the heavier weight. Oil lubricates best as certain temperatures. If you are running heavier oils and never getting the oil up to it's optimum temperature, you are actually doing more harm than good. That and that it works your OMP much harder to push that thicker fluild around (and it's even more difficult when it's cold).

If you aren't getting the oil up to temp, you are working your engine much harder which can cause certain parts to wear faster as well as hurting gas mileage. It's best to run the right weight for the right application.

 

Points taken. But once up to operating temp, and combined with fuel, I'm just not seeing those negatives outweighing the positive. But maybe I'll try some 10w-30 and see how it goes this next change. Seems like 10w-30 is on sale more often anyway.

 

Exactly, 90% of FD owners should probably be running 10w30. In all reality, 20w50 should really only be used for high power cars on the track. I can't imagine needing the higher heat range oil in street driving.

Additionally, those with a good oil cooling setup should definitely NOT run 20w50 in street driving. Even in the summer, my dual 25-row Rotary Extreme setup is running about 175-180F; in the winter, my oil temps on the highway are below 170F. I don't want to be running 20w50 in those conditions.

 

would be very interesting to have the viscosity checked after 2,000 hard street miles...I've got $100 that says it is significantly degraded

I'll stick with my Mobil 1 15w-50, thank you very much, I've been using it for years and never saw that big of a jump in oil pressure relative to other oils

after 2,000 miles it still looks pitch black, reeks of gas, and flows like water

 

What exactly do you think the positives are for running a 50 weight on the street?

 

turbines spinning at 120,000 rpm have a way of breaking an oil down pretty quick as well

they only way to find out is run a heads up test....I'll chip in for it....I think Amsoil runs viscosity tests for pretty cheap

 

Just because the oil is black and smell like gas, doesn't mean it's lost it's lubricating properties. New studies have recently been done that show today's oil lubricating properties last MUCH longer than most oil change places advertise (go figure).

The color of the oil has absolutely nothing to do with it's intended purpuse (lubricating).

 

true, but it's also true that Mobil recommends 15w-50 for "hot running" turbocharged engines, so unless new data shows it's unecessary, they have it all wrong or they are trying to sell higher viscosity oil to the public for the wrong reasons (why?)....15w-50 syn probably behaves more like a straight 30 weight under most conditions so I don't see it as a big deal, not like a straight 60 weight true racing oil or something

again, lab testing would be very informative here

 

And why wouldn't they recommend their higher priced oil? Kind of like injector companies recommending to never run past 80% duty cycle.

Unless you are spending 20+ straight minutes in high rpms with boost on the street (like you would be on a track), you aren't doing any real damage to that oil that you wouldn't be doing driving to Taco Bell (which isn't much).

 

And why wouldn't they recommend their higher priced oil? Kind of like injector companies recommending to never run past 80% duty cycle.

Unless you are spending 20+ straight minutes in high rpms with boost on the street (like you would be on a track), you aren't doing any real damage to that oil that you wouldn't be doing driving to Taco Bell (which isn't much).

 

And why wouldn't they recommend their higher priced oil? Kind of like injector companies recommending to never run past 80% duty cycle.

Unless you are spending 20+ straight minutes in high rpms with boost on the street (like you would be on a track), you aren't doing any real damage to that oil that you wouldn't be doing driving to Taco Bell (which isn't much).

 

I run 10w-30 Mobil 1 in my car all the time.
I recently noticed Mobil 1 makes a synthetic 2 cycle oil. It is rated low in ash with complete combustion, so I decided to pour a little into the tank for extra measure.

 

if your worried about your oil send it to a shop that can test it and analyze it, that way you know it didnt lose its lubrication propertys, im using 10w30 synthetic and i dont like it to much. as soon as i put it in i got bunch of sludge building up in the oil filller neck. i do tihnk my crank case filter is blocked though