Skip Howard

I'm about to switch over to Mobil 1 oil. Which weight do I use???

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85T/A 305/QJ work in progress.

ede

i think either would work but i have a hard time with zero weight oil. i know a lot of people that use it, but i've never been able to accept it. i guess that's a sign that i'm getting old when i don't like new ideas or products. next i'll be telling stories about the old days.

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ICON Motorsports

1st & 3rd

Ed Maher

Personally i'm running 5w30, and come summer i may even step up to 10 or 15. I'm a fan of heavy oil as i do a lot of long highway driving. I only went to 5w30 cuz this winter has been cold and i do have a short commute to work daily.
As you live in the so-est of soCal, run 5w30 at the minimum, if you've got a bunch of miles it certainly wouldn't hurt to run 10 or 15 (especially in the summer.) I'd rather lose a mpg and 3 hp than risk having my engine's blood run thin while idling in traffic.
...ed

Christobal

Making a decision between the two could be done by flipping a coin for all the effect it will have, especially since you're in SoCal. I believe with Mobil one, your engine will only start to see the difference between the -30s and the 15-50. In slightly sub freezing temps there is a noticeable difference in viscosity, which is bound to have some effect on cold start pumpability. You're engine is likely better off on start up wear to have one of the -30s in there. The colder it gets, the more a lower first number will have an advantage. How much better off is your engine once warm, and either cruising down the freeway, or running between 3000 and whatever thousand rpms under full load on the dragstrip? Hard to say. There is likely some benefit to having the 15-50 in there at the higher stress levels. Difference between any of the -30s is probably near nill. Mobil 1 is so good anyway, I would just choose whatever you want in a -30 if it's a street engine. If you really pound the hell out of your engine, always make sure it is at a minimum, up to normal operating coolant temperature before you get frisky, and then maybe go with the 15-50, though i believe all told, the -30s are fine even for 300-400 hp street performance and probably many race engines.
Also, if the engine is old and using more oil because of internal wear, you may see some benefit of using the thicker stuff, thouh I have run the -30s and the 15-50 in a particular engine with near 300,000 miles that is using a quart between 2500 and 3000 miles, which is not much, but much more than it used before about 225,000 miles. The difference in oil consumption has been no more than 10-15%. Probably not worth running the thicker stuff for this savings. Added pretection with the higher viscosity in this particular street application? Probably not, in my opinion.

RB83L69

How many miles does this vehicle have on it?

Since it never gets hot here at all, I'd say if less than 50k run 0W-30, 50-125k use 5W-30, above that use 10W-30 and be ready to fix some leaks. The synthetic seems to be a bit more talented than dinosaur juice at finding every little crack in the gaskets and seals and working its way tp the outside world.

I run 0W-30 Mobil1 in my nearly brand new (12k miles) 400 in my 83.

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"So many Mustangs, so little time..."
ICON Motorsports

Skip Howard

The engine has about 150K on it so it looks like I'll be using the 10W30. I'm not burning any oil with the exeption of on start-up thanks to old valve seals. I do leak oil from my front and rear seals along with the valve covers. The valve covers will be taken care of as soon as I get the spacers that's supposed to go under the bolts.

RB, can you get the "R" coded (I think that's what I saw in one of your replies) valve cover gaskets at Auto Zone??

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85T/A 305/QJ work in progress.

RB83L69

Yes, but they aren't real good about stocking large numbers of them at every store, so it's all too easy for them to be out of stock. That was the Rubber valve cover gaskets I was referring to IIRC; there are also Rubber oil pan gaskets of the multi-piece design. I personally detest cork and will not use it if I can help it; the R suffix gaskets are much more durable and less leak-prone.

Also, I recall seeing in one of Vader's recent posts (perhaps the same thread) about a GM load spreader, which might be the thing you are talking about. The pic looks absolutely identical to a Moroso one that I have been using for the last 15 or 20 years, and probably costs a great deal less than what GM charges. You can get them at your local speed shop, or places like Jegs & Summit, or maybe even carparts.com.

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"So many Mustangs, so little time..."
ICON Motorsports

JETHROIROC

Take care of the valve seals before you put Mobil 1 in, or it will smoke 3-4 times as much on startup and possibly foul your plugs, at least it did in mine. But after I changed the valve stem seals I've been running M1 5W-30 ever since with no oil consumption problems. That oil is damn good stuff.