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Old 06-13-2019, 11:33 AM   #21
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Brand: Still Looking
Model: Tiffin Wayfarer 24 BW
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"Your vehicle is designed to operate on
regular unleaded gasoline with a minimum
pump (R+M)/2 octane rating of 87.

Some fuel stations, particularly those in
high altitude areas, offer fuels posted as
regular unleaded gasoline with an octane
rating below 87. We do not recommend
these fuels.
For best overall vehicle and engine
performance, premium fuel with an octane
rating of 91 or higher is recommended.
The
performance gained by using premium fuel
is most noticeable in hot weather as well
as other conditions, for example when
towing a trailer. "

It's designed to run on 87; but 91 will make it run a little bit better...

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Old 06-13-2019, 12:12 PM   #22
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Fuel octane is a science within itself.

Going higher than 87 adds the ability to change engine timing curve increasing torque and efficiency. Octane number is resistance to detonation, higher is more resistant. Computer controlled engine that use various inputs such as knock sensors to control mixture/timing can benefit from higher octane under certain conditions. Essentially going better octane on fuel with likely give no negative effect except increased cost. Running down road lightly loaded in lighter units would probably see no benefit. Heavily loaded, towing, hot weather may see a benefit from higher octane.

I race chevy small block drag cars with fixed fuel/timing. I start out running pure 110 octane leaded race gas at $10.00 or more/gallon with new engine combinations. Then find where engine works best and start cutting the race gas with premium pump gas. I have to pull plugs and look into chambers for signs of detonation as I water the race gas down. I do this strictly to reduce operating cost. When I reach what I feel a safe I will stay at that current mix. My current setup that won NoBox/Mod class at Super Chevy Show last month at Palm Beach is using 40% race gas and 60% pump gas at 12 -1 compression ratio. I have run and won events at 14-1 on pure pump gas with reduced timing. Race gas does not inherently make car faster by itself it just allows more tuning latitude. Running pump gas with 10% ethanol does require a small increase in jet size. This is why many computer controlled vehicles saw a reduction in MPG when ethanol became mainstream. Towing with my 2007 Chevy Suburban I always used mid-grade or premium as a safety measure to minimize pinging. On more than one occasion MPG improved with addition of premium when not towing.

I did test the RV with full tank, 49 out of 55 gallons of premium and saw no net change in MPG which tells me the unit power/gearing is pretty effectively matched.

Going to better, higher octane fuel is a reasonable choice. Ford may have decided to tap any detonation reduction/efficiency improvement in heavier chassis by adding that statement about 91 octane. Plus I can see where having an extra safety margin is never bad.

This is all based on what I have seen and experienced over the last 15 years racing and towing drag car all over southeast.
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Old 06-13-2019, 02:42 PM   #23
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Quote:
Originally Posted by BandG View Post

......cut.....

So I wonder what dramatic changes they made since 2017 to make these recommendations?

I have only used 87 octane up to this point. If I ever climb the Rockies towing my Jeep, I'll probably drop a little more for the 91 octane, but unitl then, I've been fine on 87 octane.
Only F53 change I’m aware of is when Ford derated power from 362 to 320 HP, but don’t recall exact Model Year. It would have been in that time frame or a little before. I’m not sure what they changed, but could have affected their reasoning regarding octane recommendations. Torque went up a tiny bit (3 lb-ft) so who knows what was involved.


Someone mentioned compression ratio, but that’s only a small part of overall design. Some new engines with direct injection run 12:1 on regular gas, although they are way more advanced than the Ford V10. By modern standards 9.0 and 9.2 CR is low even for heavy duty trucks.


By the way, I’ve driven various V10s in Rockies using regular 85 Octane and didn’t have any issues. The only thing I do is avoid lugging an engine, which I always do no matter what. Even if it cost a little MPG, I’d rather let the engine spin at higher RPMs and lower torque. It’s an old habit I learned driving trucks with stick shifts.
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Old 06-13-2019, 02:54 PM   #24
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... And the V-10 does like to rev!
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Old 06-13-2019, 03:25 PM   #25
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Quote:
Originally Posted by Bob Denman View Post
... And the V-10 does like to rev!
I disagree. People keep saying that, but I can’t see how they come to that conclusion.

The engine does best at low RPMs, and sounds like it’s going to fly apart at high RPMs.

Everything about it except its SOHC design which it got from auto 4.6L V8 screams low RPMs. If it often spends much time at higher RPMs it’s only because it doesn’t develop enough power at lower RPMs to get the job done.

I’ve owned a couple and rented many more, but it doesn’t change my objectivity. It’s an old engine design that doesn’t develop much specific power, so it has to spin to get a large motorhome moving. It’s not because it likes to rev or that it does it well. In my opinion it just doesn’t have a choice because it’s too puny.
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Old 06-13-2019, 03:46 PM   #26
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They DO make good power up on top...
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Old 06-13-2019, 05:37 PM   #27
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While the long stroke, small bore configuration limits breathing above the 5200 redline, the design is fine for intended purpose. Think of it in terms as a sophisticated lawn mower engine. It does what is intended over a broad range of finished operating weights.

In the application I use, 2 valve in e450 performance is good. Even with trailer attached, acceleration is solid when merging or leaving at stop. MPG is acceptable at 9 to 11. Empty it may do better with a 4.30 or 4.11 gear in place of 4.56 but then performance may suffer with trailer. Overall I do not see any point trying to redesign effective architecture. The new v-8 looks good along with 10 speed trans but it would need to have a drastic improvement to pay for replacement of existing engine in my application. Just as with a diesel, trading up just is not justified on a ROI basis for me.

In the final analysis is it really worth concern when there are many miles left in our unit?
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Old 06-13-2019, 06:37 PM   #28
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Quote:
Originally Posted by Muggs View Post
.....cut....

In the final analysis is it really worth concern when there are many miles left in our unit?
I’m not saying to trade motorhomes because it’s got a V10.

My current one has just over 191,000 miles, albeit in smaller and lighter van, so I’m not refering to durability in any way. In truck applications these V10s will last twice as long as most motorhomes will ever travel before their bodies and interior fall apart or rot. But durability wasn’t the question.

Long stroke, V10 lack of balance, peak power at about 4,000 RPMs, etc. all beg to keep RPMs low. This engine “does not like to REV”.

To me, an engine that likes to rev sounds like it’s got a growl as RPMs climb asking to be pushed harder. The V10 always sounds like it’s begging the driver to take it easy. There is a reason it’s being retired. The V10 was a serious compromise Ford made to save money versus designing a new engine for HD trucks. They took a very small block V8 and stroke it as much as possible to make the 5.4L V8, and since that wasn’t enough, they added 2 more cylinders that threw balance out of whack.
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Old 06-13-2019, 06:40 PM   #29
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Ok, what I want to know, in simple English so my pea brain can handle it, Does premium increase fuel mileage or not?
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Old 06-13-2019, 06:44 PM   #30
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Quote:
Originally Posted by Bob Denman View Post
They DO make good power up on top...
Please explain how 305 or 320 HP out of 6.8 liters is “good power”.

That’s less than 50 HP per liter which is incredibly low at any RPM — on top or otherwise.
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Old 06-13-2019, 06:53 PM   #31
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Quote:
Originally Posted by Skip 500 View Post
Ok, what I want to know, in simple English so my pea brain can handle it, Does premium increase fuel mileage or not?
Not normally.

On some engines it may increase MPG slightly, but not enough to pay for added fuel cost.

If engine runs OK on regular, that’s your most economical option.
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Old 06-13-2019, 06:55 PM   #32
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Quote:
Originally Posted by Chance View Post
Not normally.

On some engines it may increase MPG slightly, but not enough to pay for added fuel cost.

If engine runs OK on regular, that’s your most economical option.
Thanks Chance
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Old 06-13-2019, 07:57 PM   #33
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The only thing I ALWAYS avoid is that crappy 85 Octane "regular" in the mountain areas of the west. The manual says 87 octane and that's what the engine gets. Not much experience with this V10 Ford yet, but my last rig a Gulfstream with the 6 L Chevy had no problems on 87 octane.
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Old 06-13-2019, 09:12 PM   #34
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Quote:
Originally Posted by Chance View Post
Please explain how 305 or 320 HP out of 6.8 liters is “good power”.

That’s less than 50 HP per liter which is incredibly low at any RPM — on top or otherwise.
I think what Bob means is that the v-10 uses its entire operational range of RPM. From 600 idle all the way to 5200 redline to meet requirements. I was passing diesels going toward Asheville N.C. last summer humming along at 4000 to 4500 RPM.

HP/litre is a good measure of level of tuning and usually also indicates how close to edge of envelope a combination is. The V-10 at 50 HP/litre beats my trailer generator at 30 HP/litre. My SBC in racecar is around 85 HP/litre. Many modern high strung engines can produce 100 HP/litre. Like I said earlier, the V-10 is in neighborhood of a lawn mower engine. Constant dependable run without compromising longevity or basic effectiveness across a wide range of loads. I would expect the V-8 with 10 speed to be an improvement but to what degree? I would not consider a new release a safe purchase until out for sometime. Ford has their share of teething problems with new platforms.

It will be interesting to see how the v-8/10 speed does but it may not match cutting edge technology of a Corvette or Mustang. Its purpose and attractiveness is not same as a sports car.
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Old 06-13-2019, 09:51 PM   #35
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Old 06-13-2019, 09:59 PM   #36
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Quote:
Originally Posted by Skip 500 View Post
Ok, what I want to know, in simple English so my pea brain can handle it, Does premium increase fuel mileage or not?
I own a gas station, which doesn't make me an expert, but I have been in the business for over 40 years, so I do know a little. As a general rule, the higher the octane, the more power...the more power, the lower the MPG. So basically premium will generate slightly more power and will reduce your MPG slightly. The increase in power as well as the decrease in MPG will be negligible so it is not likely worth the extra cost.

As for 85 octane, that is only available at high altitudes and should be fine to use if you plan to stay at higher altitudes. If you're just passing through the mountains don't fill with 85 octane.

I had a 91 Holiday Rambler and premium made a significant improvement in power but I also noticed the decline in MPG. I think the days of NEEDING premium in most any vehicle (unless specified) are pretty much over.

Almost all the premium I sell now is for motorcycles or some old guy (before you jump on me I'm 68) that remembers the old days.
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Old 06-13-2019, 10:10 PM   #37
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I've found that fuel mileage can be affected by the type of fuel being used...

... But it's tough to say exactly what might happen to it.

I've seen it go up; with higher octane
I've seen it drop; with higher octane

And I've also seen no effect whatsoever!
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Old 06-13-2019, 11:41 PM   #38
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No. The V-10 does not have a knock sensor so it doesn't know what the octane of the fuel. What does matter is the weight of the gasoline (if it is hydrocarbon). Typically 87 octane gasoline blended in the summer in non-pollution areas with 10% ethanol weigh 6.25 lbs per gallon at 20 C degrees. Non-pollution controlled summer 93 octane gas weighs about 6.20 lbs per gallon. Winter blend and pollution area blended gasoline weighs less still. So using 93 octane gasoline with theoretically decrease the gas mileage by 0.8%. Take the ethanol out and you will get about 4% better gas mileage because ethanol has a much lower heat value per pound than gasoline.
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Old 06-14-2019, 12:52 AM   #39
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Run the octane recommended in the manual. You can run a tank of super once every 10 fills or so. Super unleaded fuels add cleaning additives to them. Which can help your engine over time.
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Old 06-14-2019, 11:02 AM   #40
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Run the octane recommended in the manual. You can run a tank of super once every 10 fills or so. Super unleaded fuels add cleaning additives to them. Which can help your engine over time.
Actually all branded gasolines are rated as "Top Tier" fuels and contain the additives to keep your fuel injectors clean. Non branded fuels generally meet the minimum standards as established by the federal government. Premium contains NO additional benefits other than being higher octane...usually 91 or 93.

Therefore, putting a tank of premium in periodically serves no benefits as far as cleaning your system.
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