Best Oil for a 1975 Corvette

[gradymotorco]

I have a 1975 Corvette, with 154k miles on the body, engine was completely rebuilt at 100k, and was recently freshened up (IE, valve job, new top end gaskets, etc.) I've been running Mobil Clean 5000 10W30 in it for years, but I am curious as to whether there is a better oil for it. I change the oil in it every 1k miles/ 6 months (I never drive it, in fact I usually get to the 6 months before I get to the 1000 miles), and I finally ran out of PF25 oil filters at the last oil change. I guess I'll be using the PF1218 filter now.

Dave

 

[3putter]

With the small amount of use this vehicle sees I don't know why you would want to switch over from what you've been doing. But a really good syn blend is Trop Artic or Motorcraft (both Conoco Phillips products) at the same price as the M5000. Better profile than the straight dino you are running.

 

[Johnny]

I have bad news for you, there is not a good oil for a 75 Vette. Just ship the poor old car to me.

 

[jarvk22]

Maxlife 10w40 or Havoline 10w40.

 

[pickled]

If you never converted that motor to a roller cam setup, I'd run some heavy duty diesel oil in it like rotella or delo. You can find both in a variety of grades 15W40, 5W40 (syn) and a 10W30 if you look around at fleet stores and trucker outfits. I do believe that you can get a 10W40 Rotella as well. This is a much cheaper route than jumping over to say Amsoil AMO 10W40 or Amsoil ACD 10W30 if you aren't driving a lot in a year to push the OCI.

 

[gradymotorco]

It has a Comp cam in it, but its still a flat lifter design. Are you recommending the diesel oil because of the higher level of ZDDP? I thought that the ZDDP had been reduced in the new diesel oils too?

Dave

 

[jorton]

Took a quick look at an UOA report for Motorcraft 15w-40. It still has more zddp than energy conserving passenger car oil.

 

[HM12460]

have you considered mobil1 15w-50? 1200 ppm of zddp

 

[gradymotorco]

Well, it still has a small oil consumption problem, so I wasn't planning on running a synthetic. It also has some seepage from the oil pan and the rear main seal, so I was afraid that it might increase using a syn or syn blend. Thats the reason for the dino oil. I've always put 10W30 in it, and I still have good oil pressure, but I wonder if I should go with a thicker oil?

Dave

 

[Volvohead]

Brad Penn 20w-50 or some older stock HDEO if you can find it.

I'd steer clear of the light weight current PCMOs in that one, especially if you have a hotter cam in it.

 

[3putter]

In that case, perhaps a High Mileage Oil like Penz Bronze Bottle in a 10w40 flavor might be a great choice. Would cut down on the consumption and help swell the seals a bit.

 

[gradymotorco]

Is there really any significant difference between a High Mileage Oil and a regular Dino?

Dave

 

[pickled]

Yeah I was thinking of the ZDDP and robust additive package that these diesel oils have. Anything labeled CI-4+ is still going to have lots of the old school (ash) wear additives. As far as your seal leakage issues go, you might want to try a 10W40 HM oil for a while and see if it helps. Conversely you could go diesel and add some of the Auto Rx that everyone is bonkers over here.

 

[3putter]

Go to the Penz website and check out the Spec page of their various oils. You'll see their HM oil is at the top end of a 10w spec, and is generally a little heavier with an extra dose of additives. I've had great success with their 10w30 in my daughters '92 Maxima. It takes a lickin and keeps on tickin.

 

[OVERKILL]

I'd recommend the M1 TDT 5w40, readily available at Walmart in the 5L jugs. It's a great oil, and there are many UOA's that show it's robustness.

 

[Steve S]

The HDEOs have a pretty fair amount of zinc and phos.

 

[artificialist]

I have to wonder about the flat lifter cam issue on this car. WHen the engine was rebuilt, was some special high lift and high ramp rate cam used, or was a basic one used?

I ask, because there are thousands (Maybe millions) of flat lifter V8 and I6 engines (unmodified internally)) on the road that are doing just fine on ordinary 5w30 or 10w30 SM dino oil.

The only time I read of problems is when a very high performance cam is used, and in those situations, I'm wondering if the cams are really failing because when you push a car far beyond what it was built for, stuff usually breaks.

 

[gradymotorco]

The cam is high lift, but not excessively so. It is similar to what would have been in a late 60's Corvette Small Block, or perhaps a mildly "hopped-up" street car. Not a dragstrip cam, by any means.

Dave