I might be wrong, but I think all these new engines will run on 87, but may pull some of the timing out if the engine detonates. 89 or 91 or even 93 would allow the engine to run with a little more timing w/o the detonation, thus making more power.

 

I had a 19 6.4 and traded it on a 2020 7.3. The MDS was annoying as ****. But the truck was good looking, comfortable and I'd argue faster than my 7.3 4.30. The Ford feels a lot more like a truck.

I've grown up on ford but now my new truck needs a torque converter and possibly a transmission. Pisses me off. 5,800 miles

 

The MDS was the main reason why I didn't consider the 6.4. I also wasn't a huge fan of the rear suspension set up. I know it rides a lot better than the Ford leaf springs but that's a lot of extra crap in the rear vs. a simple leaf spring set up.

 

The 6.2 has the same octane advisory. Right in the manual it tells you to use the good stuff if you are going to be pulling, particularly in the heat and in the mountains. You don't have to use the higher octane to get the job done, but the performance will be better with higher octane.

 

they did a test again 10 months ago with the 8 speed and it still struggled. it did have 3.73s though.

 

Okay so as an owner of a 6.4 in my '17 Power Wagon (factory lift, front and rear lockers, disconnecting front sway bar, and 4.11 gears) with the 6 speed trans, I'll chime in.

Supposedly the 8-speed has made the 6.4 better. If that's the case then when properly equipped (as with everything nowadays) and properly maintained, I would hand it to the 6.4. I have driven several of the 6.2's, and while they are a GREAT engine, I don't see anything about them that would make me want to dump my 6.4 for one, even with my 6 speed. I don't really have issues with the trans 'hunting' while towing, the MDS is very unobtrusive and really doesn't make the truck sound much different - and with 4.11's it doesn't kick in very often anyway.

Do I wish it had rear leaf springs? Eh, maybe, but it's not a necessity for me and the coils give better articulation anyway, and the 3500s still run rear leafs so if you need 'em step up a size.

As for the fuel thing, mine seemed to run and tow just fine on 87. However, since switching to 91, I have noticed it pulls harder, so yes, there is an improvement when running higher octanes on these newer engines. I've also noticed an improvement in both towing mileage and empty mileage. Not a lot, mind you, but I'll take that .5 mpg.

 

For the record the 6.2's I've driven are absolute dogs compared to the 6.4. Also, my 19 2500 6.4 was an 8 speed. The trucks are great but the MDS kills it, and the fact that most people I know who are long term Mopar owners eventually need to have lifters replaced. The new 8 speed trucks engage MDS more frequently and noticably than the previous gen.

My gut is ford engineering is superior, but it's a crapshoot these days. I'm literally writing this at the dealer while I'm waiting for a ride bc my 7.3 torque converter needs to be replaced.

 

it was a 3.73 truck instead of a 4.10 truck. Even then it was max out 3/4 ton trailer wise (14k) really in 1 ton/diesel territory. If you are routinely pulling up and down the Ike at 14k I'm thinking 1 ton diesel is the default option. Otherwise I'm sure you would be fine with the 6.4/4.10.

 

There are multiple YouTube videos that discuss longevity issues with the current 6.4L Mopar, especially surrounding insufficient oiling of the valve train components.

 

I'd take it with a grain of salt, just like the 7.3: spark plug wires, leaky front crank seal, leaky oil pan, etc

 

I don’t know if the current engine offering is still that way or not but at least in 17 when I last bought a truck from them, the 5.7 did not have MDS unlike the version offered in 1/2 tons or passenger vehicles but the 6.4 had MDS, which frankly surprised me since the 392 used in the SRT/Scat Packs in chargers and challengers were significantly different from the HD v8, but I guess they shared enough R&D that it transferred over. That actually led me to buy a 2wd 5.7 2500 that ran great in the duration we drove it. We could get 17mpg unloaded all day long on the highway and it did fine towing what we had which was usually 9k or less. Had the 6.4 not have the MDS I would have ponied up the extra 1200 or whatever it was and gotten that.

 

Some have better luck than others, but it's a design flaw in the oiling of the 6.4. I wouldn't say if but when for all those mopars. Just my opinion

 

meh ive never thought it was a oiling problem. but thats the conclusion most people would arrive at when watching youtube vids.
i think it was likely the supplier of the lifters or cams was just making shotty parts. no different than trucks on this site needing new tie rod ends and tracbars at 20k mi. shotty parts my freind.
as i said before, our fleet 6.4 engines all have thousands of idles hours on each truck. i seen one couple weeks ago was near 4000 hr. no thats not a typo. if idling and poor oiling killed the engines ,i want someone, anyone, to explain why ours havent crumbled to dust

 

Just pure luck. Most of the failures are in high idle hour vehicles like cop cars. The oil for the valve train on the hemi is produced by splash, not by squirting down on them.

Again, not if but when.

 

F-250, cannot tell a difference in octane, even in high altitudes.