Community Forums

ChasA · 07-26-2013, 02:41 PM

The Ford owners manual for my previous MH. 2006 F53 chassis addressed the 85 octane found in western States. It said don't use it.

Ray,IN · 07-26-2013, 03:16 PM

Quote:

Originally Posted by theroc

That 85 and 86 octane dates back to when engines had carburetors and actually ran smoother at higher altitudes with lower octane fuel. This was primarily in the Rocky Mountain states and not in the coastal states. I'm not certain why it is even being sold anymore since there are so few carburetors around anymore.

It's good your manual specifically addresses the issue as I certainly wouldn't use it in a motorhome engine regardless.

Octane is a measurement of gasolines ability to resist pre-igniton and has nothing to do with how it enters a combustion chamber. It is very important to engine longevity. We are seldom aware our computerized engine is constantly reacting to the quality of gasoline we purchase, to prevent engine damage.

Go Dawgs · 07-26-2013, 03:27 PM

I had no problem putting in 85 octane in my MH over our 5700+ trip this summer in 12 western states. I had never seen that low of octane since the 70's and was concerned until I put it in and ran multiple tanks of it. No change in performance and no change in mileage. Unless I'm driving a high performance car, which isn't going to happen soon, I put regular old low octane gas in all my tanks and go about my trips. JMHO

edgray · 07-26-2013, 04:51 PM

Quote:

Originally Posted by awarnes

I had no problem putting in 85 octane in my MH over our 5700+ trip this summer in 12 western states. I had never seen that low of octane since the 70's and was concerned until I put it in and ran multiple tanks of it. No change in performance and no change in mileage. Unless I'm driving a high performance car, which isn't going to happen soon, I put regular old low octane gas in all my tanks and go about my trips. JMHO

Could you please add your chassis / motor to this discussion

Ray,IN · 07-26-2013, 05:24 PM

Quote:

Originally Posted by edgray

Could you please add your chassis / motor to this discussion

He tells all about it, here: http://www.irv2.com/forums/f87/new-t...-a-147383.html

Magumba · 07-26-2013, 09:29 PM

I haven't noticed a performance problem even though I've been using the 85/86 octane gas. Of course if I was using 87 octane I might have climbed some of the hills faster.
Fingers crossed that I have not damaged the engine.

Chowboy · 07-26-2013, 09:55 PM

The ECM will adjust for owners failure to comply to recommendations. There may be consequences in mileage, performance but the engine should not suffer other than reduced spark advance.

cucamelsmd15 · 07-27-2013, 05:43 AM

Quote:

Originally Posted by RustyJC

Actually, the ECM (ECU) will retard ignition timing when it senses detonation (knock). Retarding ignition timing lowers peak firing pressures and reduces the tendency for the fuel/air charge to autoignite, although at a loss of fuel efficiency.

Rusty

You lose more than fuel efficiency by pulling timing. The fuel efficiency change is relatively small. As a related note, in addition to pulling timing, most ECUs will also add fuel to richen the mixture as a method to cool the intake charge.

The biggest thing lost with an ECU pulling timing is torque. A good rule of thumb for a N/A motor is every degree of timing pulled is worth about 5ft/lb of torque. That doesnt sound like much, until you realize that the ECU generally has 20 degrees or so of control authority over ignition timing. It usually depends on the base timing in the map itself, but 20 is a nice round number Ive seen time and time again. And for something like a Ford V10 that has 457ft/lb at peak torque, losing 100ft/lb is significant. Even more so when you realize that at 10,000+ft, that 457ft/lb has quickly dwindled because of elevation.

Go Dawgs · 07-27-2013, 08:01 AM

To follow-up on questions on my Chassis and trip. I have the 3500 cutaway chassis GM van with the 8.1 Vortec engine. We traveled over 5700+ miles in 12 western states. Washington, Oregon, CA, AZ, NM, TX, OK, Kansas, CO Utah, Idaho, Montana. All types of condition, good and bad roads, wind, rain, thunderstorms, hail, etc. Had to run both AC for over 2/3 of the driving part of the trip due to 95+ heat, not used to that being from the PNW. During all that I ran into many different octane levels which I hadn't seen since the 70's. Didn't notice any performance issues at any time and the only 2 things that effected performance and mileage was wind and running the AC's. Lowest mileage was 8.6 (climbing into the Grand Canyon and running all AC's, and 8.1 running into a head wind in Kansas and both AC's. High was 10.8 in Northern Idaho and Montana and 10.6 in western Texas, no wind. Overall was 9.78, which was about .5 more than I though I would get on average. Used cruise most of the time, unless climbing and tried to stay about 61 or 62 for speed. I've been driving for almost 40 years and have traveled extensively in the Western US and I'm no expert on engines I have logged over 500,000 miles. Gas is gas, in my opinion, on most vehicles and though an extreme high performance engine may require high octane most regular engines don't. Burning 91 or higher octane may get you some benefits I believe in the overall big picture the extra cost isn't going to save you money. Again JMHO.

Technobody · 07-28-2013, 06:55 AM

Here in Ontario regular gas is all 87 octane middle is 89 high is usually 91 however Sunoco also has a Ultra 94. I have never noticed any difference between regular and mid. But I do with Sunoco Ultra 94

Magumba · 07-28-2013, 06:57 AM

After leaving Americas Campground in Box Elder SD yesterday morning we stopped at Flying J next door for gas and propane. I noticed this placard on the 85 octane pumps.
Also the 85 octane does not have ethanol and it was 20 cents more expansive then 87 octane which I pumped. In my future troops out west I'll use 87.
Thanks for an interesting discussion.
Happy camping.

Libero · 07-28-2013, 07:20 AM

Quote:

Originally Posted by hdossett

Tom, could you provide a source for this information. My V10 dose not do well on 85 octane. If I have a tank of 87 and go to higher elevation, 10,000 feet or more, the engine runs just fine, even after sitting for a few weeks. Once I filled with the lower 85 at higher elevation and then came down to 1,000, and the engine did not run smooth until I mixed in some 89 to bring the octane level up to 87. My V10 calls for 87.

Just wondering.

H

Where are you driving above 10,000 feet in an RV? Colorado?

**CLIFFTALL** · 07-28-2013, 07:26 AM

The Eisenhower Tunnel in the Rockies is over 11,000.

Lifemember · 07-28-2013, 07:32 AM

Features

Most cars use "regular" gasoline, which is usually 87 octane. Regular gasoline is some areas of the U.S. is 85 octane. The yellow sticker at the gas pump states the octane level of the gasoline. You should not use 85-octane gasoline if your owner's manual recommends a higher octane level.

Considerations

Lower air pressure at high altitudes lowers the pressure in your car's cylinders; this might allow you to use a lower octane fuel. Eighty-five octane fuel at high altitudes is equivalent to 87 octane at sea level, according to Car Talk.

Effects

You are using an appropriate level of octane gasoline if your engine does not make rattling or pinging noises. Switch to a higher octane gasoline if the engine rattles or pings.

Misconceptions

Using a higher octane gasoline than recommended by your owner's manual won't improve gas mileage, make your engine cleaner or improve engine performance, says the FTC.