Mixing Pennzoil Syn Blend and Havoline Dino

[TR Graham]

Gents,
This is my first post. However, I have been a long time lurker on this board, and have learned a great deal of useful information. I have a few questions I would like to pose to you all. My new girlfriend recently bought 5 qts of Pennzoil 10W-30 Synthetic Blend and one qt of Havoline 10W-40 Dino for use in her beater 1992 Chevy Lumina w/ 3.1 V6. (don't ask - to her, oil is oil...)

Personally, I have reservations about using a synthetic (even a blend) in her high mileage engine, so I am going to get her the GM recommended straight dino 5W-30 to run in her car. However, this leaves me with 6 qts of perfectly good oil, which I am thinking about using in my truck (a 2002 Toyota Tacoma w/ 3.4 V6, currently using Mobil 1 5W-30 and a M1 filter)

Now, my questions are - what would be the effect (if any) of mixing one qt of 10W-40 dino oil with the synthetic blend 10W-30? I drive my truck from GA to TX (887 miles one way) at least once a month . If I do use this mix, any ideas about how soon I sould change it? I typically change the M1 oil and filter I now use at between 8000 to 10000 miles. I did a search, but found little to answer my questions.

 

[Islandvic]

What is the sump capacity of the Taco?

I would mix but not make it a habit.

IMO a 5-6k mile OCI should be okay with your oil combo.

Go back to your nice M1 diet afterwards.

Good luck!

 

[Bryanccfshr]

I would run what your GF bought in her car. No need to take your Taco off what has been working for it for an interval just to burn off a little oil.
I am certain that the Lumina will run fine on the synthetic blend penzoil. The havoline would be good top off fluid for her car as well. I had that 3.1 V-6 in a 92 Sunbird and ran that to I think 120k on Quaker state before I moved on. THe Semi syn wont cause it to leak or anything.

 

[Blue99]

The Pennz 10W-30 syn blend is a GRP II/GRP III dino blend and mixing with 1 quart Havoline 10W-40 should not be a problem.

This mix will be a slightly thicker 10W-30, and from your description - I'm assuming the bottles are GF-3 - the add packages will be relatively similar compared to some of the newer GF-4's we are seeing.

Run it in either vehicle for 4K miles & not to worry!

 

[haley10]

I'd run the Pennzoil in her car. It won't cause any problems at all. OK to mix the Havoline or use for topping up. My GM dealer puts a Mobil synthetic blend in everything that doesn't require full synthetic anyway. You won't have any problems with it.

 

[High Plains Drifter]

You could just return the oil and get some Mobil 1 or whatever she needs

 

[pitzel]

Lol, its a 3.1L. Seriously, if you can keep the coolant out of the oil, pretty much any oil changed every 10k miles will give you 300k+ miles. With a synthetic such as M1, 20-25k miles sounds about right.

What you need to watch out for with that engine is the oil pump drive seal. It is where the distributor is traditionally mounted. Instructions for replacing the seal are found at http://www.w-body.com . Its not a hard procedure, but you have to remove the throttle body (pain in the rear considering you have to remove some coolant lines), the fuel supply, and various other fasteners to reach the actual oil pump drive seal.

edit -- actually the 1992 3.1L MPFI isn't all that susceptible to the intake coolant leaks. Nowhere near as bad as the Dex-Cool filled 3100/3400 engines built a few years later.