I have been reading several forums now regarding the use of Mobil 1 Truck and SUV 5W-40 in a Jeep 4.0L. Asside from what the used oil analysis say, why do you guys recommend this oil in the 4.0? The reason I'm asking is because I have a 98 Jeep Grand Cherokee 4.0 with 84,000 miles and am now thinking about switching over to the Mobil 1 Truck and SUV stuff. Is there a noticeable differnce in how the engine runs?
Why use 5W-40 in a Jeep 4.0?
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I don't have an UAO to back my recomendation, but my 97 Grand Cherokee 4.0 110-k seems to really like the 5w40 Truck & SUV.
My milage has only dropped less than .2 mpg from the previous Mobil 1 10w30. I only use this vehicle to take care of my rental property and the occasional snow day in Oklahoma. So I like the thought of a HDEO in the crankcase.
I will most likely pull a used oil analysis on the 2nd run of the Mobil 1 Truck and SUV.
My milage has only dropped less than .2 mpg from the previous Mobil 1 10w30. I only use this vehicle to take care of my rental property and the occasional snow day in Oklahoma. So I like the thought of a HDEO in the crankcase.
I will most likely pull a used oil analysis on the 2nd run of the Mobil 1 Truck and SUV.
I think the UOA is the primary reason to switch to a heavier weight oil in the 4.0. Iron numbers tend to be high in lighter weights.
That being said, I never noticed any difference in the drivability of any of my Jeeps no matter what oil was in them. But I do prefer to keep the UOA numbers as good as possible for longevity purposes.
I want to see some used oil analysis on this in the 4.0. The only one I've seen so far was't much, or any better than mine with Chevron 10W30 High Mileage.
That one showed pretty high lead, so I'd like to see more.
That one showed pretty high lead, so I'd like to see more.
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I think it really depends on your type of service that you subject it to. If it's a short trip usage type ..then the oil never get to a high enough temp to reach its spec'd visc.
Some assert that the Fe is from ring/cylinder wear ..others have suggested that it could be the timing chain
I know in my usage, the difference between M1 xw-30 and Delvac 1 5w-40 was to the tune of about a 60% drop in Fe numbers over like OCIs (around 10k each).
Unless you do some sort of longer commute ..then I wouldn't recommend using a 40 weight. There's no gain to it when your 30 weight is probably still at a 40 weight when you turn off the engine. It takes about 13-15 miles to get the oil up to any real temp.
Some assert that the Fe is from ring/cylinder wear ..others have suggested that it could be the timing chain
I know in my usage, the difference between M1 xw-30 and Delvac 1 5w-40 was to the tune of about a 60% drop in Fe numbers over like OCIs (around 10k each).
Unless you do some sort of longer commute ..then I wouldn't recommend using a 40 weight. There's no gain to it when your 30 weight is probably still at a 40 weight when you turn off the engine. It takes about 13-15 miles to get the oil up to any real temp.
The earlier Jeep 4.0L engines had an infamous "piston slap" issue that 40-wt oils help quiet.
These engines also have extremely loose tolerances, hence the preference for heavier oils.
With that said, many 4.0L engines have surpassed 200k on nothing but 10w30 conventional, so it's not like a 30-weight oil is going to send it to an early grave.
These engines also have extremely loose tolerances, hence the preference for heavier oils.
With that said, many 4.0L engines have surpassed 200k on nothing but 10w30 conventional, so it's not like a 30-weight oil is going to send it to an early grave.
My used oil analysis w 40w oils have been better in my 2.5L TJ and brother's 4.0. The 40w cut my iron wear numbers in half compared to the Mobil 1 10w30 that was in there before. No decrease in fuel economy was noted.
You can look at my old used oil analysis on our 2001 L6-242 XJ. Ran Mobil 1 10w30 to about 40m, then a couple of Mobil 1 0W-40s (a thick 30W). Changed to REDLINE 10w30 for the next 50m (totalled at 95m). Engine was better than new, as good if not better than at 30m.
I've run both 10w30 (5w30 in winter) and 5w40 in my '88 Jeep Cherokee. I netted very little change in gas mileage and an insignificant difference in wear metals between the two weights. I have noticed since swtiching back to 10w30 that my idle has smoothed out again.
I'm back on the 10w30 usage for the time being. As pointed out, there are a ton of these engines that have lasted forever on 10w30, so that isn't hurting anything!
My used oil analysis are posted if interested...
I'm back on the 10w30 usage for the time being. As pointed out, there are a ton of these engines that have lasted forever on 10w30, so that isn't hurting anything!
My used oil analysis are posted if interested...
**These engines also have extremely loose tolerances, hence the preference for heavier oils.**
Actually the tolerances(I ssume you mean bearings) are no different than any other engine. The issue with 258's,4.0L's, and 2.5L's (which is in my YJ), is the non-adjustable valvetrain that tends to make more noise as the engine wears. The 2.5L also has a "slider" style timing chain tensioner which adds to the noise as well (and some of the higher Fe levels).
I usually run 10W30 in my 2.5L and run 10W40 when I have a trail ride and it's warm outside. The 40wt definitely quiets it down a bit. 40wt oils have come a long way and I've always liked a thicker oil in my rigs.
Actually the tolerances(I ssume you mean bearings) are no different than any other engine. The issue with 258's,4.0L's, and 2.5L's (which is in my YJ), is the non-adjustable valvetrain that tends to make more noise as the engine wears. The 2.5L also has a "slider" style timing chain tensioner which adds to the noise as well (and some of the higher Fe levels).
I usually run 10W30 in my 2.5L and run 10W40 when I have a trail ride and it's warm outside. The 40wt definitely quiets it down a bit. 40wt oils have come a long way and I've always liked a thicker oil in my rigs.
The good old 4.0 I6 is based on really old school design princeapals. It was specked for heavier oils by todays standards from it's intial inception. History has shown that it likes 10W40 and the 5W40 recomendationis just an improvment on the old 10W40 recomendation.
The 4.0 I6 usualy consumes oil at a quicker then apreciated rate with most 5W30 and 10W30 oils. Your iron will also drop in most cases when you switch to a 5W40.The 5W40 also has better cold pump,flow numbers over the 10W40.
The 4.0 I6 usualy consumes oil at a quicker then apreciated rate with most 5W30 and 10W30 oils. Your iron will also drop in most cases when you switch to a 5W40.The 5W40 also has better cold pump,flow numbers over the 10W40.
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