'75 CJ5 AMC 304 oil?

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Recently picked up a '75 Jeep CJ5 with an AMC 304 V8. This is my first AMC engine, and first V8 in a Jeep. Speedometer has been changed out to a newer model, so I have no idea the mileage. Any suggestions on an engine oil and weight?
 
Rotella T 15W-40 would be my recommendation. It has earned high praise from folks familiar with those old AMC motors.
 
How’s the gas mileage on that 304? I had a IH Scout with the 304. The two are different engines but get confused for each other.

I got 10mpg on a good day.
 
Originally Posted By: PimTac
How’s the gas mileage on that 304? I had a IH Scout with the 304. The two are different engines but get confused for each other.

I got 10mpg on a good day.
the 345 in my scout got 11mpg. The 392 in my 1210 got 5.5
 
Originally Posted By: Chris142
Originally Posted By: PimTac
How’s the gas mileage on that 304? I had a IH Scout with the 304. The two are different engines but get confused for each other.

I got 10mpg on a good day.
the 345 in my scout got 11mpg. The 392 in my 1210 got 5.5




My Scout was a 1979 model year. That engine had the old air pump and all sorts of junk to help with air pollution. The horrible Holley carb they used then didn’t help either. I heard those 392 motors were real gas hogs.
 
15w40 isn't a bad suggestion in warmer climates. I restored a '79 CJ7 with a 304 in it earlier this year - didn't rebuild the engine, just new seals and gaskets, and put Schaeffer's 7000 10w30 in it and it ran very well with it. A syn blend 10w30/40 would be my choice - Valvoline Maxlife, Rotella T5, Schaeffer's, or other.
 
I used to help with a 304 Gremlin. Real happy with 10w30 Dino back in the day. I would run a compression check and pull a valve cover to inspect the inner valve cover, etc. I like MaxLife. Rotella 15w40 seems to do well in the flat tappet motors...
 
My 1979 CJ-7 w/304 gets 13 mpg on the highway. It's stock w/31" tires. I use Peak 10-30, Smitty's 5-30 or whatever is laying around. It does not seem to care.
 
Any stock AMC V8 is not hard on oil. They are cream-puff motors. They can be built into pretty impressive engines, but in OEM form, they are mild. Nice little motor. A 360 AMC weighs identical (within few pounds) and will make that little JEEP a real toy
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If it were me, I'd prolly run Maxlife syn-blend (Red Bottle) and a good filter and call it a day.

If you want all year oil for say 2-year oil changes (low mileage), maybe a 0W-40 would be a good start. The cam and lifters are well broken in, so anything with 800 PPM ZDDP will be fine. It won't care about the name on the container
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If it won't sit out and have to start on cold winter days, and you are happy with a 30 at OP Temp, maybe Delo 400 15W-30 SD (severe duty) as about one of the stoutest premium dinos out there with plenty zinc for any need
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401's are a wee bit hard to come by. But if you run across one, why not
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No goofy kid cams or anything like that. Jeeps like mild motors that will lug through tough spots. SO it's all about good workmanship and real good fuel/air control. Holley center pivot carb for side hilling and have it jetted on a chassis dyno so it's spot on. Should be good for 13+ MPG as long as you don't mat it all the time
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Hi @Jason280. We suggest using Rotella T4 Triple Protection for your 304 V8 engine – Rotella T4 Triple Protection 10W-30 for temperatures down to 0 deg F, or Rotella T4 Triple Protection 15W-40 for temperatures higher than 30 deg F. For year-round protection you can also use our fully synthetic Rotella T6 5W-40 oil.
 
Thanks for the information, seems like I have a few good choices to pick between. Temps here in Georgia aren't too severe, we rarely see temps much lower than 20* in the winter.

As far as the mileage goes, I really don't know...I haven't driven it enough to really calculate anything. I really wouldn't call it a slug, either, feels like it has more than enough power for the little CJ. My '94 YJ has a 4.0L 6 cylinder, and even though its rated at more HP, it feels like the 304 is a little stronger off the line. Of course, the YJ only weighs around 3300lbs, and I'd bet the CJ is under 2800 lbs, so its not like it needs a lot of power!
 
I've used HDEO 15W-40 in my AMC 360 over the past ~7 years from Rotella and Delo.

Recently I'm using Farm store brand HDEO. For me, that's Harvest King HDEO 15W-40 from Rural King. Here is a VOA that I had done on the oil before putting it into service: https://bobistheoilguy.com/forums/ubbthr...0_#Post4414794. I believe Harvest King to be made by Citgo.

There's been no perceived difference between these three oils (how it should be). Any oil available today is MUCH higher quality than oil back in the 1970s when this engine was new. I like 15W-40 for the higher oil pressure (about ~15psi hot idle for me). HDEOs should be more robust against fuel dilution that could happen with a carburetor.
 
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