Using Mobil1 15w50 On the Street During Warm Weather

[ZapperZ]

About to do my oil change thinking about adding Mobil1 15w50 for the street.
My driving is aggressive so I feel that the extra protection would help.
I always allow the engine to bring up oil pressure after starting.
Any thoughts on this?

[zcarczar]

That's all I run in mine, supposedly it will affect your fuel economy but I don't think its much of an issue.

[macalot]

Originally Posted by zcarczar

That's all I run in mine, supposedly it will affect your fuel economy but I don't think its much of an issue.

I have been running 15w50 the last 2 months, no problem but I do let it idle to warm some as the bar pressure is up there at startup.
Doesn't seem to affect the fuel economy. I've had two trips in neighboring mostly flat Ohio, one with factory spec oil and the other I just did with 15w50. Cruise control set at 74 mph in 6th gear...Mpgs were both essentially the same 21.2 and 21.5 mpg. 21 mpg in this beast...Too good to be true, but it is! Now get into the mountains/hills of W. Pa and I get around 19 as advertised.

[WoodBoss]

With 15w50, the 15 number is for when the oil is at ambient temp not when it is hot after running. The 50 weight the thickness or viscosity number after it is warmed up. Use Amsoil 5w30 and you will be better off. When you first start your car is when the most wear occurs. Bob is the Oil guy wrote a good bit of information regarding what oil to use. I doubt you will use 15w50 after you read this. Good Luck


http://www.bobistheoilguy.com/motor-oil-101/

[macalot]

Originally Posted by WoodBoss

Use Amsoil 5w30 and you will be better off.
http://www.bobistheoilguy.com/motor-oil-101/

When the Official GM Track spec sheet says use 15w50, that's what I use...so I drive the same oil on the street as well as the track, no big deal.
Now in the colder weather I'll change back to 5w30 and of course it won't be tracked at all or driven much then.

[White_SS/RS]

Can't go wrong with what GM says, however WoodBoss has a point. Many of us track guys have tested different oil viscosities and we've found through track testing and oil analysis that the 5/30 provides adequate protection and reduced oil temps over heavier oils such as 0/40 and 15/50.

[X25]

My post regarding this on Corvette Forum is below.

Long story short, GM does not recommend this for street, and you're supposed to replace it back (with 5W-30) once you're done with the track day. If it did not have side effects and has better protection, our cars would come pre-filled with it.

Originally Posted by X25

That's the main guideline by Bob (Bobistheoilguy) as well. As such, 15-20 PSI at idle is more than enough. Keep in mind, you care about flow, not purely just the oil pressure. We use the oil pressure as an indicator for the flow that does the lubrication, not the other way around. The thinner oil will have less back pressure (and will flow faster as well), and it does not necessarily mean it's providing less protection.

The LSX engines are meant to run on oil with 10 cSt viscosity (the viscosity of 30 oil at operating temp; 212 degrees F). In an ideal world, we would have 10 cSt in every temp, and engine and the oil pump would be very happy.

When you use very thick oil, it creates so much back-pressure that the oil pump just bypasses the oil back to the sump at cold starts, significantly reducing the flow. Again, keep in mind, it is the oil flow that lubricates, and the pressure is indicator of flow, and a very false indicator at cold start. The bypass gate starts opening up at a very low 50 PSI on LS3s as far as I know (Camaro). As such, with very thick oil, and especially if you use it all the time, your engine will have a very accelerated wear in daily use, which is why these engines never come prefilled with that oil. GM recommends replacing the oil back after the event anyway.

Viscosity of 5W-30 at 302 degrees F is around 3.1, 0W-40 at 3.7 or so, and 15W-50 at 4.5 or so. None of these are close enough to 10 (what engine is designed for), so all will fall short. The important point here is that 3.1 viscosity at 4.5 viscosity are not light years apart; just 2 cSt. You can't just divide one with another, and say that it gives 50% better viscosity at 302 degrees F; it would be misleading. Remember, at 100 degrees F, the OEM oil will be around 50s cSt while the 15W-50 will be at 125 cSt(!!!!); way too thick, and the viscosity difference is 75!

15W-50 should never be used for street.

[X25]

If you really really really want to use 50-weight oil daily, perhaps you should use this one
http://www.ebay.com/itm/291530807111

[Mikebrinda]

Originally Posted by X25

My post regarding this on Corvette Forum is below.

Long story short, GM does not recommend this for street, and you're supposed to replace it back (with 5W-30) once you're done with the track day. If it did not have side effects and has better protection, our cars would come pre-filled with it.

+1. In this instance, I got to roll with the guys with the mechanical engineering degrees who built the machine. I mean, if they don't know for sure, who does?

[Lightsaber]

Originally Posted by X25

My post regarding this on Corvette Forum is below.

Long story short, GM does not recommend this for street, and you're supposed to replace it back (with 5W-30) once you're done with the track day. If it did not have side effects and has better protection, our cars would come pre-filled with it.

Thanks for the info! This has been much informative!!

[X25]

Originally Posted by Lightsaber

Thanks for the info! This has been much informative!!

I'm glad to be of help. I used to think that the best oil would be 0W-50, or 5W-50, which would be the best possible in all temps, but it turns out I couldn't be more wrong. For a synthetic, 5W-50 will mean that it'll be more like a straight 50 weight oil than anything else, which happens to be only a tiny bit more fluid than its regular 50 weight cousins (like 15W-50 referenced here) to still pour when very cold, and way too thick for our cars. In short, you can almost ignore the first number; it's the (high temp) base weight that significantly determines the characteristics of synthetics.

[ZapperZ]

By the way I'm fairly experienced with synthetics as I have had offshore powerboats with BBC's for over 20 years. .
Question also does the LS7 Z/28 have high oil temp on the highway under hot weather and aggressive driving?
I'm new to LS7 and need to learn what's best for them.

[Quasimofo]

Originally Posted by ZapperZ

By the way I'm fairly experienced with synthetics as I have had offshore powerboats with BBC's for over 20 years. .
Question also does the LS7 Z/28 have high oil temp on the highway under hot weather and aggressive driving?
I'm new to LS7 and need to learn what's best for them.

What is a high oil temp? I'm new to v8's in general. I saw a bit over 200 in oil temp sitting in 95 degree high humidity stop and go for a few miles, with all stock fluids.

[X25]

Originally Posted by Quasimofo

What is a high oil temp? I'm new to v8's in general. I saw a bit over 200 in oil temp sitting in 95 degree high humidity stop and go for a few miles, with all stock fluids.

212 degrees F is the ideal oil temp, and it is what the car manufacturers usually shoot for. Enthusiasts usually like to see it a little lower than that. I like it around 190s, but you should keep in mind that the oil needs to hit 212+ degrees F often to burn/evaporate the contaminants.