6,8 V10 vs 7.3 V8 performance

Dave W · 02-10-2022, 06:15 AM

We are starting to look for a preowned Greyhawk (26Y) and I'm curious as to whether there is any real difference in the way these engines perform. I have a fair amount of experience with a 3 valve V10 in a 5th wheel tow vehicle(F350) but none with the 2 valve version in anything. Is the gas mileage about the same (7-9mpg loaded)? Maintenance factors about the same?

I apologize if this has been answered, my search couldn't find a similar thread

dxrobertson · 02-10-2022, 07:18 AM

I believe my 2021 Entegra 26D is near the same as the Whitehawk 26Y. I have the V8 and average 10MPG towing a 2500lb car and average 11MPG without towing.

The maintenance for the V8 is pretty simple up to 30K miles:
oil, filter change at 10K mile / 1 year
brake fluid change at 3 year
air filter at 30K mile

From removing the engine cover inside the cab and looking around, it seems everything is accessible (plugs, etc).

foglght · 02-10-2022, 08:06 AM

I found the 7.3 to have better mileage, by about 1mpg. The trans calibration was/is not good. Pedal is sometimes non responsive. The new engine seems louder at lower speeds around town, but the V10 seemed really loud in upper RPM.

Example: On ramp taking it slow and when I get it sort of straight punch it to try to get up to speed. 3-4 seconds of no response from the trans and then maybe it will downshift.

I bought the 5 star tuner for it. Wrote a whole article on it as well.

Midwest Jeffk · 02-10-2022, 11:42 AM

I own a retail business and have owned dozens of fords over the years. The V-10 has been a proven venerable workhorse for the last 30 years. Known to be reliable up to 300,000 miles or more. I also have the V-10 in my 2016 Greyhawk with 30,000 miles on the clock. The business now has a 2021 E450 gargo box truck with the new 7.3L. Initial complaint by driver is the V-8 is noisier/louder. However power is good. Both are high revving engines that produce similiar torque. Point is you can't go wrong with the V-10. It has been a great motor for a long time. If it was me I would let them work out the bugs on the V-8 a little longer. Good luck.

foglght · 02-10-2022, 11:45 AM

The V8 engine "redlines" at 3,900rpm in the motorhome chassis. If you get the 5 star tune it jumps to 4,800.

CAG · 02-10-2022, 11:58 AM

Quote:

Originally Posted by foglght

The V8 engine "redlines" at 3,900rpm in the motorhome chassis. If you get the 5 star tune it jumps to 4,800.

One has to wonder what kind of strain that additional 900 rpm puts on the engine and transmission? The original engineers must have thought 3900 was best or they probably would have made it go 4800.

foglght · 02-10-2022, 12:22 PM

Quote:

Originally Posted by CAG

One has to wonder what kind of strain that additional 900 rpm puts on the engine and transmission? The original engineers must have thought 3900 was best or they probably would have made it go 4800.

Unsure. There could be any number of reasons from cooling capacity to laziness (cost cutting). It could be that the catalyst gets too hot in the motorhome chassis with the carryover piping (if its the same). The only way to cool it down is to spray fuel at it, so instead of redesigning the exhaust and reprogramming they keep the same exhaust and limit RPM.

It could be that the E450 grille opening wouldn't support high rpm running at max GVW/GCW and they didn't want to spend the money to redesign the grille as it was likely never rolled up in the cost of the refresh.

The same motor gets used in the F53 chassis with a max GCWR of 30,000lbs, so maybe it isn't the cooling.

The HP/torque rating is "just" above the old engine. The same engine in the trucks makes 430hp, but its backed by the 10 speed auto and not the 6 speed the motorhomes use.

The same engine in the trucks revs to almost 6k.

Since these are commercial chassis, they could have derated on purpose based on durability dyno cycles that they ran showing limiting RPM can significantly increase engine life.

Could be anything.

When I was developing a vehicle, I wanted a lower tire pressure for better ride quality given our new tire. Changing the placard pressure on a vehicle requires a whole lot of money and time to certify and nobody wanted to spend the money even though it significantly improved ride quality.

Dave W · 02-10-2022, 02:12 PM

Thanks folks. All good info.

The higher noise level of the 7.3 surprises me as my old pickup with the 3 valve V10 was anything but quiet especially with 12K plus hooked on the back as a 5th wheel and going up a long grade with the 5 speed transmission of 2006.

3900 rpm for the 7.3 seems ridiculous as my current 6.7 diesel is red lined at 3600 with max torque/Hp rating at 2800. Is that max torque/horsepower rating or a "one more rpm and it blows up" number?

It really makes no difference which one is in whatever we buy, I just feel the need for some basic knowledge before we make the leap.

Jopopsy · 02-10-2022, 05:31 PM

I’ve owned 4 Class C coaches with the V10 (5 and 6 speed) as well as my current coach with the V8. I’ll take the V8 any day.

CAG · 02-10-2022, 05:50 PM

Quote:

When I was developing a vehicle, I wanted a lower tire pressure for better ride quality given our new tire. Changing the placard pressure on a vehicle requires a whole lot of money and time to certify and nobody wanted to spend the money even though it significantly improved ride quality. __________________

I have mentioned it before in threads about tuning. A developer of one of the major tuning programs used for Duramax said, when asked about the dangers of tunes. Any change from the original program in the vehicle leaves the vehicle open for damage, no matter how small. It is cumulative and eventually damages or destroys the engine. Question is when? Perhaps not in your time owing the vehicle but down the road. You as the owner have to decide if you can live with that result. Speculating whether the developer of the vehicle decided not to make improvements due to cost is just that, speculation and all of the rest is a WAG.

Sorry, I did not mean to drag this off topic but it does pertain to the engines in question.

Lake Huron · 02-10-2022, 06:37 PM

I drive a 2020 F450 7.3 w/10spd. Like previously posted throttle response is poor. Its almost caused me an accident. When I stand it to the floor I want power now, not in 3 seconds and then have to wait for it to get rpm's up because its locked into 3rd gear and wont downshift. The trans constantly skips 2nd and 4th gears on up shifting. I've had to seriously change the way I drive it. Wife has a G6, daughter has a Trailblazer, I daily drive a Yukon and the tow vehicle is a 3500 Duramax. Suttle changes have to be made in how each vehicle drives, i get it, but the F450/7.3 is a totally different animal. I dont like it. Yes, the 7.3 is louder than the V10's, but I will admit it really does sound good.
My work buddy has a 13 F450 w/v10 and 170k on the clock. My 20 7.3 has 30k on the clock. Both vehicles are really close in weight and just for kicks we ran them off from a stop.

Which one won???

Neither. My green light response was slightly faster than his so I got a little jump on him, but he never lost ground and I didnt gain any either. We ran them up to 60 and quit, didnt want to draw too much attention and get in trouble. Lol!

foglght · 02-11-2022, 11:44 AM

Quote:

Originally Posted by CAG

I have mentioned it before in threads about tuning. A developer of one of the major tuning programs used for Duramax said, when asked about the dangers of tunes. Any change from the original program in the vehicle leaves the vehicle open for damage, no matter how small. It is cumulative and eventually damages or destroys the engine. Question is when? Perhaps not in your time owing the vehicle but down the road. You as the owner have to decide if you can live with that result. Speculating whether the developer of the vehicle decided not to make improvements due to cost is just that, speculation and all of the rest is a WAG.

Sorry, I did not mean to drag this off topic but it does pertain to the engines in question.

While that can be true it is not always true. Especially for diesel vehicles. You can only add so much fuel before you get smoke which with a DPF clogs it quickly. NOx emissions are critical as well and are heavily regulated. EGR significantly reduces NOx, so much of the performance of the vehicle is clamped down compared to a non restricted/emissions vehicle.

In many cases once those are removed the engine can run more performance without sacrificing engine durability. Problem is, its illegal.

ActionJackson · 02-16-2022, 01:01 PM

After 3 Class C rigs with the V-10, we bought a 2021 7.3 rig. Way better power and drive ability, IMO. No more downshifting going over overpasses on a flat road. Less rpm and engine noise. Better MPG by 1 to 1 1/2 MPG. More power up hills with less rpm. Win, win all the way around.

pnevells · 02-16-2022, 04:43 PM

My old greyhawk 31DS had the V10 we pulled a racecar trailer all over the eastern US with it no complaints averaged 7.5 MPG . We bought a 2022 greyhawk 30 Z with the V8 i am getting about 8.5 MPG pulling the same rig , I like the V8 better, it is noisier on rapid accelleration but it has better passing power

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