Needing Oil Advice...

[1991Jeep_Man]

I'm actually nervous about posting this in the first place due to the possibility of an all out oil war, but here it goes.

My '91 XJ has about 210k miles on her. Everything thus far has been kept up to date and taken care of. No leaks, no overheating, coolant change, oil change (mobil 1 High Mileage 10w30 for the longest time), etc. Now, with my recent oil change I used Mobil 1 High Mileage 10w40 rather than 10w30. Honestly, I was surprised by the results. My oil pressure, while never really low or anything, seemed more stabil and slightly higher, and when the engine reached op temp, some of the little noises I used to have seemed to either lessen or go away completely. Loved it. However, I am more concerned now because after reading many oil articles and what not, cold startup is the biggest wear and tear moment on an engine. And I will be honest, both the 10w30 and 40 had their share of cold start noises. My solution? I want to run a good 5w40, especially with colder weather among us here in Shenco. Now, this is where I will say I am not looking for an oil war or flame debate. I have basically narrowed my choice for oil down to two oils:

Mobil 1 Turbo Diesel 5w40, or Shell Rotella T6 5w40.

Which would you all suggest? From I've heard and researched, both oils are good, and many people run diesel oil in their 4.0's (although, I must admit I dont agree with those who swear by 15w40 and 20w50). So which oil do ya'll think I should go with? Btw, I currently use a Mopar oil filter. I know PureOne filters are supposed to be the best, but I actually had one of their filters suffer an internal failure and reduce my oil pressure rather drastically. New filter solved the problem, and Puralator determined their filter did in fact fail. If anyone has a good suggestion for an oil filter for these oils, please chime in! Thanks everyone.

 

[Shorty]

both are good oils and I wouldn't hesitate to use either of them. Include a quality filter and see how it goes.

Out of curiosity, why don't you agree with a 15w-40/20w-50?

 

[1991Jeep_Man]

both are good oils and I wouldn't hesitate to use either of them. Include a quality filter and see how it goes.

Out of curiosity, why don't you agree with a 15w-40/20w-50?

The cold weight just seems really thick to me. I mean, I can understand 15w40 in hot climates, but I've seen people who run it year around, and I can't imagine it's good during cold start, considering some guys suggest running 0wXX for much faster flow during cold cranking.

 

[Wayne Sihler]

My 96 now has 341,000 miles on it, It has had a steady diet of 10w-30-in winter months, and 15w-40 Rotella T in the rest of the year.

Over its life it has used Texaco,Shell,Castrol and maybe a shot or two of Valvoline.Next oil change it will get the green jug Castrol GTX in 10w-30.

The wifes 98 has gotten a steady diet of green jug Castrol GTX in 10w-30 for its life .(250,000)
A good quality oil filter--Purolater or wix and regular changes leads to a long happy life....

 

[cruiser54]

You guys really over think this oil situation...........How much thicker is 20 weight oil than 10 weight oil when it's cold? We used 15W40 at the dealership all the time when these Jeeps were new because the owner's manual said you needed 15W for if it got down to zero and 40 weight if it got to 100. It was all illustrated in a nice handy chart in the manual. Here in the mountains of central Arizona, we could see both extremes. Sold and maintained LOTS of Jeeps with 4.0s with no issues whatsoever. I run Rotella 15W40 to this day year round.

 

[Shorty]

The cold weight just seems really thick to me. I mean, I can understand 15w40 in hot climates, but I've seen people who run it year around, and I can't imagine it's good during cold start, considering some guys suggest running 0wXX for much faster flow during cold cranking.

I've been using 15w-40 year around here primarily based on the suggested oil in the owners manual. It recommends 20w-50 down to 30*F and 10w-40 down to 0*F. I have sort-of split the difference with a 15 weight on initial start up, but I've never actually seen a 0*F day around here:spin1:

I don't know if the newer (Chryco written) manuals recommend the same, but I'll trust AMC to have known what the engine needed in 1988:cheers:

 

[cruiser54]

I've been using 15w-40 year around here primarily based on the suggested oil in the owners manual. It recommends 20w-50 down to 30*F and 10w-40 down to 0*F. I have sort-of split the difference with a 15 weight on initial start up, but I've never actually seen a 0*F day around here:spin1:

I don't know if the newer (Chryco written) manuals recommend the same, but I'll trust AMC to have known what the engine needed in 1988:cheers:

My point exactly. Thanks, Shorty. Joe Peters was right about you.

 

[WB9YZU]

Don't over think oil and maintenance. Unless you drive in extremely hot conditions a 40 weight simply reduces your gas mileage. Follow the owners manual and use a good quality 10W30 and filter, and change both every 3K.
For winter use you could go to a 5W30 and have excellent results.

If you are running a true synthetic, you should be able to reduce the weight even further and still get the same protection.

-Ron

 

[1991Jeep_Man]

Another reason I really want to stick with the XW40, is because when I switched to 10w40 I had reduced oil consumption as well.

 

[Johnnie Walker]

I use Amsoil AMO 10w-40 with added zddp. If it comes time for an oil change and I don't have any left I'll use Pennzoil Platinum or Ultrain the same weight

Don't over think oil and maintenance. Unless you drive in extremely hot conditions a 40 weight simply reduces your gas mileage. Follow the owners manual and use a good quality 10W30 and filter, and change both every 3K.
For winter use you could go to a 5W30 and have excellent results.

If you are running a true synthetic, you should be able to reduce the weight even further and still get the same protection.

-Ron

I call BS on the mileage loss of the thicker weight oil. I have run both 30 and 40weights in my Heep and few that I used to own. Mileage never decreased when I used 40weight. I only used 5w when I was up in Washington state. And in my bug here in so cal I run straight 30weight.
And the properties of the oil do not change the viscosity of the oil, just because it has better protection does not mean a 30weight is as thick as a 40weight.

 

[1991Jeep_Man]

After much more research between Mobil1 vs Rotella T6, I have decided to roll with the Rotella T6. I'll pick up two gallon jugs (to fill up, and the rest keep just in case) and either continue with the Mopar filter or may even use a Wix one. Any objections to the filters?

 

[Ecomike]

I never use anything but K&N oil filters now.

5W-30 versus 20W50 issue has more to do with where you live, and how much wear the engine already has on it. I have one very old worn engine, and I live in Houston where we hit 105*F record days for nearly 6 months in a heat wave from hell this year. And I almost never start my jeeps at ambient temps below 30*F here. So I use 20W50 on that engine. Also at peak temperatures 20W50 barely holds 17-18 PSI on that engine at a hot idle once it is fully saturated with heat. If I use 15W40 or lower it eats oil like gas, with 20W50 it barely uses oil. Also that engine (4.0 AMC 1987, 287,000 miles), has a high capacity oil pump already.

You did not mention the peak to peak temperatures where you live?

Lastly, keep in mind that the newer low range viscosity oils (less than 15W40) have far less ZDDP than 15W40 or 20W50 in general. The diesel oils have a little more ZDDP that the gas engine only oils in general, all other things, like the API label spec on the bottle, being equal.

 

[Johnnie Walker]

After much more research between Mobil1 vs Rotella T6, I have decided to roll with the Rotella T6. I'll pick up two gallon jugs (to fill up, and the rest keep just in case) and either continue with the Mopar filter or may even use a Wix one. Any objections to the filters?

I mainly use Napa Gold filters (made by Wix, but usually lower priced), Wix or Donaldson filters. All good quality.

 

[blubullett]

I mainly use Napa Gold filters (made by Wix, but usually lower priced), Wix or Donaldson filters. All good quality.

Napa Gold, Wix, and Motocraft FL1A's are all made right next to each other at RACOR/Parker Filtration in Modesto CA. All are the best quality filters you can buy. The Motorcraft ones are usually under 3 bucks at Wallmart.

 

[b5blue]

I use Valvoline Racing Oil, "off road rated" it's got good ZDDP ratio for flat tappet cams. NAPA Gold filters provide better flow on my 4.0 engine. I use the same in my 70 Charger's 440.

 

[Talyn]

I never use anything but K&N oil filters now.

K&N is made by Champion, same as Mobile1 and others.

 

[Ecomike]

K&N is made by Champion, same as Mobile1 and others.

Even if that is true, the specs are completely different.

 

[Talyn]

Even if that is true, the specs are completely different.

Going off of what?

 

[1991Jeep_Man]

Thanks for all the advice and suggestions everyone. I guess my oil filter question was geared more towards if Rotella needed a certain filter or anything. Anyways, based on popular vote, I think I'll grab a Napa Gold filter this oil change. Thanks again!

 

[Jeepguy03]

Good choice on the Rotella. Either oil is a good choice, but I find the Rotella to be a little cheaper at least around here. UOAs (used oil analysis) show that the 4.0 turns in lower wear numbers with a 40 weight oil. Some of the best UOAs have been from Rotella T6 5w40 and Mobil 1 Turbo Diesel Truck. Heavy duty engine oils seem to do best in the 4.0. Rotella also makes a T5 10w30 semi-synthetic HDEO for those of you who want to stick with a 10w30.

Being in a climate that gets colder during winter I find that a 5w40 synthetic is perfect for year round use. My 4.0 even seems a little quieter. My mpg was unchanged when switching to a HDEO.

With our motors, its important to have a good anti-drainback valve. A Wix or Napa gold filter is fine, Mobil 1, K&N, Purolator, Motorcraft and other good brands will work well. Avoid Fram filters.