standard, synthentic?
Posts: 293
standard, synthentic?
81' gas flap. Sept build. 14k miles. Mostly original. Updating things...
Location: FL
Posts: 947
My VIN: Early
Early 81 5spd conversion- DMCH Ground Effects, Double Din, Custom Instrument Cluster, QA1 Suspension, 3.0 PRV with MS3
Location: Northern NJ
Posts: 8,576
My VIN: 10757 1st place Concourse 1998
The engine was made to use standard oil, syn is overkill and unnecessary. There are anecdotal cases of old motors used to ordinary oil that when switched to syn, started leaking because the seals get hardened and allow the syn to leak faster. The most important factor is regular oil changes with a good brand of oil.
David Teitelbaum
Location: FL
Posts: 947
My VIN: Early
Early 81 5spd conversion- DMCH Ground Effects, Double Din, Custom Instrument Cluster, QA1 Suspension, 3.0 PRV with MS3
Same here, I use Castrol GTX 20W-50.
I wrote the attached note in 2013 for a previous post. I still use Mobil 1 10W-40 High Mileage Oil and the OEM long block has about 15,000 miles on it now.
Location: Taylors SC
Posts: 5,326
My VIN: (former)05429
Club(s): (DMWC) (DCUK)
Our normal go-to oil is Castrol 20W-50. If you are the typical low mile driver and change it every year/3000 miles it should be fine. This is the official company recommendation.
Having torn down a few engines at this point, I'm most impressed with high mile engines that have been running synthetic oil. If you are doing that I typically use Mobil 1 15W50. NOTE this is my opinion based on observation and personal use. Mobil does not recommend synthetic in this engine probably because they have not tested it. Do this at your own risk.
I also recommend against changing to synthetic oil on an engine with unknown history and/or without a look under the valve covers. I have seen an instance where a somewhat grungy engine was switched to Synthetic, and the grunge inside started to come loose and plug things up. If there are deposits on the inside of the engine stick with the regular oil, and change it more often.
Dave S
DMC Midwest - retired but helping
Greenville SC
Location: Rochester, NY
Posts: 276
My VIN: 1776
I use Brad Penn 20W50. It is basically the old green Kendall GT1, made in the former Kendall refinery. It has a high zinc content by modern standards, which may be beneficial for our cams and rocker arms. Castrol GTX 20W50 is also well-regarded.
I bought my D with 22,000 miles on it and I run MOBIL 1 since. Last year I did valve gaskets and could not believe how clean the valve covers were. I've rebuilt many other engines in my life and valve covers always have a lot of gunk in them.
Dave M vin 03572
http://dm-eng.weebly.com/