My '65 389 holds 6 quarts with the filter. Original pan and dipstick. My '67 GTO holds 7 quarts with filter. Original pan and dipstick. I use the long Wix filters and Shell Rotella 15/40 diesel spec oil, and have since about 2002. Prior to that, it was Kendall 10-30, no longer available. Run a high zinc/phosphorus oil like the diesel spec stuff, or the classic car stuff. Racing oil does not have the additive package needed for stop and go street use, nor the anti-corrosives. It's made to be run hard at the track and dumped.
If I were in a colder climate, I would run more expensive 10-30 high zinc boutique oil like Brad Penn. As hot as it is where I am, however, the 15/40 has been just fine. Many folks like to specify really heavy 20/50 oil, but for an engine that's set up to stock specs and not worn out, it's a bit thick.
I don't run synthetic oils in any of my old cars, and haven't in the 40+ years I've been driving them.
Just for fun, the next time you change oil in the '67, only put 5 qts in the pan. Then remove the dipstick from the '65 and check the oil fill level. If both pans are the same, and have the same capacity, the 5 qt dispstick will read Full with the 5 quarts in the '67 pan. This would mean that the 6 qts is 1 qt over full and your '67 has a 5 qt pan + 1 filter for 6 qts.
I am sticking with a 5 qt pan and 1 qt filter, but always fill to the full line after you run the engine as some filters are larger/smaller.
The SD 421's used a higher 6 Qt capacity pan. I emailed Butler about this as they rebuild a lot of engines, and the reply was that they did not see any differences in the pans and thought they were all the same capacity.
And, in all the engine build books, including some golden oldies, none of them recommend or mention to find the 1-year only 1967 GTO oil pan because it holds 6 qts of oil versus the standard 5 qts.
The question of oil and filter capacity has been asked a couple times here in clarifying the correct amount. The confusing part is that some will say 5 quarts in the pan plus 1 for the filter making it a 6 quart system. BUT, another person may say that the correct amount is 6 quarts in the pan and 1 for the filter making it a 7 quart system - and they would be right based on the year of their GTO. This conflicting info deals with the 1965-67 model years.
With the introduction of the 1968 model, all Pontiacs use 5 quarts in the pan and 1 quart for the filter.
A service bulletin was issued by Pontiac in 1966. It clearly states that the oil capacity is 6 quarts in the pan and 1 quart in the filter. GTO owners will tell you that their dipstick clearly says 6 Quarts at the fill line - so yes, this is fact, according to the Service Bulletin, but maybe there is a reason for such a bulletin and it may not be because a larger pan was used. Yet when a 5-quart dipstick is set side-by-side with a 6-quart marked dipstick, they are identical in length. There is no difference in the pan, they are all seemingly the same. Hmmm, so what gives?
An earlier problem with low oil pressure in the 1961 421CI HO engines was noted by a PY member and falls in line with the later GTO problem and the 6 qt pan fill:
"A couple months ago I was reading the Craftsman Service News, and found a recommendation for a 421 HO that wanted you to put in an extra 1/2 Qt and make a new full mark on the stick. Reason was accelerating hard may cause a loss of pressure."
A PY forum member stated that he had talked with Milt Schronack of Royal Pontiac fame and he stated that Pontiac was replacing a lot of 1965 GTO engines under warranty and it was found that the engines were being burnt up due to lack of oil. The owners were pushing the engines hard and at the upper RPM's much of the oil was being pumped up to the top end and not leaving enough in the pan to oil the bottom end - especially if the oil level fill level had been allowed to get low. So Pontiac issued a service bulletin to fill all engines with 6 quarts plus 1 quart for the filter. They also used a dipstick having the 6-quart fill mark. This extra quart helped keep enough oil in the pan and prevent the engine from running out of oil and burning up.
So this bulletin and change was for 1966, but owners of 1965 and 1967 GTO's have also found the 6-Qt stamped dipstick. It is quite possible that when the car was brought to a dealership to be serviced and the oil/filter changed, the 5-Qt dipstick was replaced with the 6 Qt stamped dipstick so as to protect Pontiac from having to cover warranty engine work.
PY member response:
"However, it may be up to interpretation: Nobody runs w/o an oil filter. The indicator says 6 QTS, that would be with oil filter mounted. Drain the pan, change filter, pour 6 QTS in total and check indicator.
Have the same 5qts stick as you posted , also have one marked 6qts. same identical length just scaled up higher."
PY Member Pinion Head:
"All the Pontiac V8 non-AC indicator rods I have noted are 17 3/16" from the tip to the bottom of the Bell shaped cup that covers the tube.
First version I have is inscribed "- DO NOT OVERFILL - USE GM MS OIL "
this style, I believe, is earlier than 64.
2nd style here is is inscribed 5QTS-DO NOT OVERFILL- USE GM -60641-M QUALITY MS OIL
believe from parts I pulled with it, that version is '66-67.
The non AC indicator rods marked " - 5QTS - DO NOT OVERFILL- USE SE ENGINE OIL" are '68 & later.
Am measuring 3 3/16" inch to the full line on all of the above versions."
Another Pontiac pan/dipstick oddity in 1964 as noted by a PY member, "But in '64
everything got the same pan (4-qts) and upper tube. 389, 421, HO and GTO all got the same pan and upper tube but the 421, HO and GTO (were to get 5+1 of oil)
got a different dipstick to measure the difference." In other words, the 4-qt pan was overfilled 1 qt and Pontiac used a differently marked dipstick to show 5 qts in a 4 qt pan.
If I ever get the chance to purchase a known 1966/67 GTO factory oil pan at a reasonable price, I will get it and measure its dimensions and fill it with oil to confirm the actual oil capacity.
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