I have a 1981 with a fairly new motor. I want to switch over to synthetic oil, but was wondering if I should use 10W-40 since I only use the car during the summer months? Its stored away from September until April every year. Car only has 3,000 miles on new crate motor. I only drive it about 400-500 miles a year. Thanks for any suggestions.

 

At 400-500 miles a year not sure what the benefit of synthetic oil will get you. I use Mobile Delvac 1300 15W-40 diesel oil in my 65.

 

In my eyes, synthetic can't hurt it. I run synthetic in mine and change it every thousand miles since it sits so much. I've also been told I way overdo things, so take that as you want

 

 

My 81 has flat tappet.

 

look for oil with CJ-4 or CK-4 API specification

 

 

You need synthetic oil for two reasons:
1) The lubricity and reduced wear rate of synthetic oils (compared with regular oil) is MUCH better;
2) Synthetic oil won't "age" while it's just "waiting for summer".

If you feel you need to add zinc for a useful purpose, have at it. I think it's a waste of money for a stock-built '82 engine.

 

Yes sir, I too would agree that synthetic based engine oils can't hurt but I don't see them helping over and above a quality conventional engine oil in this particular scenario. This observation is based on a study we did several years ago for a major engine manufacturer. Oils were sampled twice a month (as I recall) and submitted for analysis. The study involved multiple engines over a two year period.
NOTE One important consideration for long-term vehicle storage is routinely starting the engine and bringing it to stabilized oil temperature.

Synthetic formulated engine oils, by definition Base Oils, are blended with API Group 3 and/or 4 base oils. These oils really start to demonstrate their performance qualities under adverse operating condition, e.g., high engine temps/thermal oxidation.

Diesel formulated engine oils do bring added ZDDP to the package and thus can affect the anti wear and oxidation properties. On the downside they can be more viscous. Higher viscosities are known to decrease power and increase operating temps. Both of these changes are relatively minor but measurable. In addition to SAE 15w40, there are also 10w30 and 5w40 diesel grades. The 10w30 oils are often blended with Gr 2 and 3 base oils and 5w40 with Gr 3 and 4, whereby placing them in "semi synthetic" and "full synthetic" categories, respectively.

I would also add there many engine and engine oil tech savvy folks on this forum and their advise is well noted.

Vic

 

My engine builder on my 78 L82 says to use Valvoline VR-1 20w-50 racing oil which I just changed to after having the Driven Breakin Oil in it for 1000 miles. I think it has even more ZDDP that the Rotella oils.

Also before the rebuild I used the Castrol 10w40 EXtra Mileage oil for many years. But this was with all original parts (cam etc) that had been well broken in with oils that had ZDDP in them.

 

I like your engine builder's thinking! Valvoline VR1
Vic

 

I agree

 

Mobil one 15w 50. Has the most zinc/ phosphate and you can get 5 gallon jugs at walmart for less than $25. They list it as high performance oil for flat tappet

https://mobiloil.com/~/media/amer/us...pecs-guide.pdf


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That racing oil is thick, but has zinc at 1300 PPM. The other Walmart Mobil 1 choice is the 0w-40 euro-spec at 1100 PPM. This is what I use, though both are a strong buy when I'm at Walmart. I haven't seen the 0w-40 lately.

 

For summer, for a 1981 with flat tappets, I'd go with Penn Grade 1 in 15W40.

If you have a roller cam and roller lifters installed, you could go with just about any 15W40 (most are "diesel" oils, but that's fine for these engines).

 

Thanks everyone. I went to Advance and got a 5 quart jug of Mobil 1 10W-30, full synthetic. It was on sale and not much more then the conventional oil.

 

what was the API service rating. in the end that is all that maters, any thing else is hype and marketing

 

I have been using Brad Penn for years with no issues of any kind.

https://www.penngrade.com/about-us/

Cheers!

 

The API rating is GF-5,SN