Engine oil

[hanger]

So I’ve been using Valvoline 10-30 conventional in my 87 GW 360 since I bought it 5 years ago and now am unable to find it. What kind of oil are you guys using. I can’t seem to find anything but synthetic. I had read somewhere synthetic is bad for these old engines. I appreciate anyone’s experience and input on this.

[Scotty54]

Opinions (and real life experience) are all over the map on this. It used to be my first priority to change over to synthetic motor oil. About 10 years ago when word came out about reduced zinc in synthetics (and mineral oils) I switched to diesel oil, same viscosity. Now even that may have reduced zinc so I switched to high zinc racing oil, specifically Brad Penn Motor Oil. Now that company has been purchased and the oil is no longer what it was, so I am back to good "old" synthetic. I use Valvoline high mileage synthetic in my Cherokee 401. No particular reason other than good reviews on forums. I have no brand allegiance. I actually use three different brands in my four vehicles, due to age and mileage and manufacturer's recommendations. My Mazda and Chevy Colorado are very specific about oil.

I have had lots of vehicles that leaked oil, but never had a non-leaker turn into a leaker due to synthetic oil. My experience has been more of viscosity than oil makeup. If it leaks, try a heavier viscosity. It won't stop the leaks but may slow them down a bit. 10W30 is great if you don't leak and don't burn oil. If either issue presents, just increase viscosity. Most leaks are easy to fix but for rear mains - I just don't worry about those like I used to.

This topic had lead to all out war on some forums. Fortunately this is a great forum and a topic of constant interest and you will get useful (and respectful) comments here.

[sierrablue]

I use 10W-40 in mine--mostly for the added zinc over 10W-30. These older pushrod engines really need/like zinc to make their cams last. The Valvoline Daily Protection stuff is pretty good, although I'd buy whatever the parts store has if it leaks much.

[tgreese]

I'd think you could substitute 5W30 for 10W30 with no difference, even if you have to use synthetic. There are plenty of 5W40 oils too, which might be an even better choice. The "W" means "winter" which means that the oil has viscosity like single grade 5 wt oil at freezing temperatures. Still gets thicker with reduced temps, just not as much thicker. Being "5" instead of "10" would seem a good thing. The oil has viscosity like single grade 30 wt at higher temperatures. Pretty sure this change results from improvement in the design and production of the oil molecules that give the multivis properties.

Supposedly the diesel oils have more high-pressure additives like zinc (ZDDP) because the wrist pin loads are higher than gasoline engines and they need to address that. These loads are similar to cam flat tappet loads we are worried about re low ZDDP in our older engines. I don't think they've eliminated the wrist pin loads, but instead have developed high pressure additives other than ZDDP that don't corrupt catalytic convertors like ZDDP can. Likely I will go to 5W40 Rotella T6 for my Jeep's next change.

Regarding "synthetic" it's still oil, but made from various oil feedstocks and additives. Pennzoil specifically puts "made from natural gas" on its synthetic oil, which is still a petro-hydrocarbon. A popular story says that synthetic oil will leak more than conventional oil ... maybe. I'd be more inclined to blame old hard seals than the oil.

[rocklaurence]

I use the 20-40W Diesel oil and a bottle of Zinc additive. You can normally get diesel oil a little cheaper than the gas oils because diesels use so much more oil during a change and people dont like the added expense of all the oil.

[Kowpie]

I would agree with what Scotty says about this question on other forums. Folks really get nasty sometimes. Also agree that this forum tends to be different and a tad more refined. As for me, I use Rotella T-4 15W-40 in both the 258 and 304 with zinc additive. Maybe an overkill with the additive but I just removed the intake manifold on my CJ-7's 304 after 11 years of use and 60,000 miles from a complete overhaul. I pulled all of the lifters for an inspection of the camshaft and lifters proper. All components looked as fresh as they day they were installed. Good results here with diesel oil and zinc additive.

[candymancan]

I use whatever is cheapest.. so i just use walmart stuff 10-30 or 10-40 for all my Jeeps.

My 360 rear main leaked badly too for 6 years.. so no point in using exoensive oil if it lost a quart every 200 miles. I did the rear main again a month ago... still leaks.. not as bad this timr.. but i give up on the rear main.

Itll keep getting cheap oil.

Our 4.0 on the ZJ has 400k miles.. and the last 100k or so ive used wal mart oil.. no issues.

[sierrablue]

I've been thinking about going to diesel oil (sticking with 10W-30 or 40 if I do). Anything thicker than 10W-40 is excessive IMO, but I know a lot of people who run thicker. It's gonna hurt mileage and maybe be pricier, but it shouldn't hurt anything. HOWEVER, I would caution that a thicker oil may be hard on the starter, and possibly make it not start in the extreme cold.

I realize some switch it out for thinner oil in the winter--and it may be helpful, however, mine cold starts at -25°F with the 10W-40, and comes all of the way down to the 40psi that it's supposed to when it warms up.

I respect the other ways of doing it, this is just what I do, and it seems to work OK.

[yz400e]

Second on the Rotella T-4. it has the necessary quantity of zddp additive.

If you don't want to get diesel oil, you could always buy a bottle of zddp when you do an oil change. There are many brands. Here is a link to an 'article' on Speedway motors. I'm sure they are pimping the brands, but there is some science in there that may be of use.

https://www.speedwaymotors.com/the-tool ... ough/32478

[J20Hunter1]

Lucas oil has a Zink additive we used it in race engines good stuff

[67GMC]

We still get the Valvoline Conventional 10W30 up here. If I can't find that, then I use Pennzoil Conventional. Have used this for years in Cherokees, Wranglers, and the Wagoneer. I have thought about Rotella but it's a little pricey. For the miles I put on them the oil is changed before I hit the mileage mark so I think it's got pretty good lubrication.


On my newer cars (VW/Toyota) I've been using the Walmart Supertech Synthetic. It's pretty cheap and rated in the middle on Bob is the oil guy site last time I looked. Seems ok.

I'm sure we are all changing the oil, filter air filter way more than these Jeeps ever got done in the 70s or 80s! I remember my mum saying to me how much she loved her '77 Buick. Nothing ever went wrong with it and she never had to change the oil . LOL I cringe when I think of that poor engine. Quadrajet carb was probably full of carbon etc. Oh well-We have the internet now and people then only could go by what their mechanics and friends told them.

[oldironneverdies]

Why not Use Rotella dino 10-30 diesel oil. It has the higher levels of zinc, and maintains the same viscosity you have been using. I would not suggest anything heavier than 15-40 due to the added strain on the distributor gears driving the oil pump in cold weather