So I was checking out the Mobil website and was shocked to see that they recommend 15W-40 oil for a 82 Trans Am ??

That's the same weight as some heavy duty trucks and equipment !!!


Been using 10W-30 for years, But I do have low oil PSI



Dave

 

On my turbo motor i use 15w-40. I also used it in my high mileage 305 that has low oil pressure. It gave me a good 10 psi more pressure at idle over 10w-30

So if you have low pressure it could be worn bearings. Motors losen up some over time. Thicker oil can help

 

It is also possible that they make the 15W-40 with different additives for flat tappet cams

 

I run 10w40 premium protection Amsoil in my 86. Runs great.

It's going to run just fine. The 40 is has a higher film strength and will protect better in higher temps and under higher loads. It will slightly impact fuel economy.

You could run 20w50 and it would be fine. We run 15w50 Dominator in all our race builds. But make sure you warm them up for 15 minutes prior to heavy loading.

Engine Masters (look it up on YouTube if you dont understand) ran a 300 HP 305 on the Westech Dyno and threw NOS at it till a piston detonated at way over 600 HP and they used 15w50 Dominator. This was on a stock bottom end. Amsoil reccomended it for the heavy NOS loading due to its incredibly strong film strength.

Now if 15w50 were too thick for the bearing clearances it certainly wouldn't work at 600 HP on a stock 305 bottom end.

GD

 

Shweet thanks for the feedback guys !!!!!!!


Local red.neck farm store has 15W-40 Lucas oil for $16 !!! Gonna change it this weekend

http://www.atwoods.com/ta-oil-fluid-...l-1-gallon.htm


Dave

 

BING! BING! BING!

Look at the zinc and phosphor content of the 15W-40 "High Mileage" Mobil 1 and you may see the difference.

 

I have a feeling they are taking diesel oil which has 1200 ppm of zddp, and repackaging it as high mileage oil.

I have been using Rotella in both my Vette, and my Camaro.

 

Rotella no longer has adequate levels of Zinc and Phosphorus for flat tappet engines.
I use an additive. That way, I know the high-pressure anti-wear additives are actually in there.

 

So far I've been using Mobile 1 5W-30 synthetic with a Zinc additive in my flat tappet cars.

 

Does this Mobil one come with the zinc additive or are you adding it to it? I have been using 5-30 pretty much in all my vehicles so I started using it in the Z. Should I be adding Zinc?

 

I add it. If your car is stock, you should have a roller cam and should be okay.

 

What's a flat tappet cam? Sounds like something a caveman would drive. What's next? Clutch fans? External voltage regulators? V-belts? 6V charging systems? Points?

 

See attached. 2017 data from Exxon Mobil
also: https://mobiloil.com/en/search?q=zddp
BTW, if you have a flat tappet camshaft, you're looking for about 1200 ppm Zn.

 

lol honestly I like clutch fans

 

lol honestly I like clutch fans

You are not the only one.

 

0W-40 or 10W-40. Thanks, I'll have to stock up on some. But even the 5W-30 I usually use has 900 PPM of Zinc.

 

Engine Masters did a clutch fan vs electric fan dyno test. The clutch fans suck enormous amounts of power. Like 20+ HP. Electric fans are definitely for the win.

https://www.google.com/url?sa=t&sour...jtvfnGP_UlkifA

GD

 

I contacted Shell last week. I asked the rep about zddp levels, and he told me that Rotella zddp level is still 1200 ppm, and they have not reduced the zddp levels, and they are the same as previous years. I encourage you to do the same if you have doubts.

I had the same concerns, but I am content that it's safe for flat tappet engines as it has been in the past.

 

I did the same a few times they have been 1200+ zddp for a long time

 

Rotella T6 VOA indicates otherwise:

https://bobistheoilguy.com/forums/ub..._rotella_t6_5w

Zinc: 1140, Phosphorus: 982

It's not bad, but it's not over 1200. Here's what I use and reccomend:

Amsoil Premium Protection 10w40.

Zinc: 1368, Phosphorus: 1265

GD

 

Could also be a weak oil pressure sender. Probably more common than worn bearings.

 

I agree. Usually bearings worn enough to cause any significant pressure drop are probably not long for this world.

Generally speaking (engines in general) pressure drop is usually a result of some kind of pump issue, pressure relief valve, or some high pressure gallery seal, etc (assuming it's *real* pressure drop and not just crappy plastic stock gauges and unreliable stock sensors). If bearing clearance goes to poo the engine will begin knocking in pretty short order as wear like that tends to accelerate pretty quickly if it's resulting in significant pressure drop. You would also usually see evidence of this type of failure in progress by cutting open the oil filter, etc.

Contrary to what people believe - unless the engine is run out of oil, or run with contaminated oil, etc - the wear that occurs in bearings is typically very minor. They are designed to trap and hold (embed) contaminants and if the oil film is maintained with enough volume and pressure then basically no wear should occur. Most engines die because they got ran out of oil through consumption - fouled and weak rings, valve stem seals, etc cause consumption and the engine gets run low on oil - even a short loss of pressure will cause significant damage to bearing surfaces if the engine is under a load.

GD