2006 ranger v6 3.0L mfi at $2.99 a gallon can I switch to 85 octane? it's not a flex fuel vehicle. would there be any problems doing this?
I guess if they use it at high altitudes like Denver then there would not be any harm using it at sea level as long as the engine doesn't ping with predetonation.

 

I did some checking and seems your engine is equipped with a knock sensor. so if it detects knocking it would retard your timing to keep it from knocking, you'll lose some performance and some MPG though, so maybe it aint really worth it. PS what the heck is predetonation? did you mean preignition?

 

As far as I know, the Ranger 3.0L OHV does not utilize a knock sensor...

Pinging is the primary concern when using lower octane fuel.

 

85 octane is developed for high altitude use for vehicles that lack the ability to adjust for altitude automatically (carburated vehicles, some early FI systems). Your car automatically knows what your elevation is, and adjusting timing and fuel accordingly, under the assumption you are running the factory specified fuel. Your owners manual calls for 87, so thats what you should run.

Those that argue that it doesn't hurt to run the lower octane often don't really know. From what I've seen even if it doesn't cause knocking and pinging, lower octane fuel burns hotter and faster at lower compression than high octane fuel. This means your exhaust valves get hotter if you run too low and octane, and this in turn causes the seats to fail and valves to warp.

You will get better performance, fuel economy, and engine longevity running 87.

 

I can't argue with the physics Khan notes, but think that the marginal difference in temperatures would not be notable except in marginal conditions, and would take a long time to have an effect. I did not even know about the 85 octane availability until traveling cross country where it was sold at altitude in NM & AZ. The lowered octane takes advantage of the lowered density of air at altitude. The MAP and MAF know about this to a degree, and adjust fuel appropriately. I"d guess there just isn't enough air per volume to have any long term effect. Most ignorant of altitude systems cannot adjust the mix, and they would be too rich, keeping the burn cooler. Smarter systems adjust as best they can and again seem to have met manufacturers specs.
At sea level, I'd bet there could be a good chance for pinging.
tom

 

You would think, but I'm talking about experience. I live in SLC, an area where we have 85 Octane as low grade.

Lower octane fuels aren't just less resistant to detonation, they burn hotter and faster. Now you can argue the air is less dense, so it would offset. Again, on a vehicle that cannot compensate for altitude, such as an older carberated vehicle, the lost density will nt cause them to run rich, the correct amount of fuel is drawn in because relative vacuum is unchanged. Its just that the vehicle uses the same timing as it otherwise would at a lower elevation. The result is a significant drop in performance, as elevation increases and desity decreases, you need more timing advance to try to maintain a reasonable level of performance, and a lot of it has to do with emission. Basically reducing density has the same effect as increasing octane.

Now on FI vehicles that use MAF sensors, or vehicles that have a BARO sensor, they know about elevation changes, and they adapt automatically, assuming that you are still running the same octane. Basically as elevation increases, they calculate a new timing curve. Now if you put in 85 octane, and it is designed to run 87, and it advances the timing, you have just created a perfect recipe for pinging. Even if you don't get pinging, the burn temperatures will rise dramatically, and here is an additional factor.

As air density decreases, the amount of air passing through the radiator also decreases. And the amount of heat that the air that does pass through can carry decreases. This doesn't just affect the radiator, it affects every component that relies on air to cool it, which is ultimately everything. So as elevation increases, the engines ability to reject heat decreases. This is one area where our oil company and EPA policies of putting out lower octane fuels is bad.

I deal with a lot of mechanics shops, and deal a lot with a good machine shop. When people run 85 in vehicles designed for 87, it shows up in the form of valve wear and hot spots. The differences are not marginal.

Read your owners manual. If the manual says to run 87, thats what you should run. If it specifically says you can run 85 at higher elevations, then you are fine in doing so, but all of my Fords specifically say not to.

I also have a turbocharged car, and it is designed to run 93 from the factory. Getting 93 is difficult around here. Turbocharged cars are not really affected by altitude changes. As altitude increases, the turbo just pulls in more air and compresses it. The problem is actually the opposite, as altitude increase, the octane requirements also increase. This is because the turbo will still compress the air to maintain the correct levels of boost, but the efficiency of the turbo decreases, so the amount of heat it produces increases. Then because the air is less dense, the intercooler does not work as efficiently, so the air charge doesn't get cooled as much before entering the engine. I am in the fortunate position to have an aftermarket computer, so I can tune the car to run as correctly as possible on a lower octane, which is done mostly by pulling timing. And my setup is altitude aware, so it adjusts automatically for changing elevation, which again, really has little effect, I recently pulled over a pass at 9600 feet, and other cars were showing serious decreases in power, yet mine from a performance standpoint felt unchanged, other than the temp gauge was running a little bit hotter than at lower elevations.

For the record, I tested running 85 in my 4.0L Aerostars. Both of them would ping on hard acceleration with 85, they ran perfectly on 87. On my '95 Chevy C2500 it will run on 85 without pinging, but it gets better performance and economy on 87.

 

Oh really, this is the pic I see looking at Alldata

 

Then it looks like Ford added a knock sensor somewhere along the line. Maybe on account of all the pinging complaints they had with that particular motor. I was not aware of the change, thanks for the correction.

One thing I will say though, is any Ranger 3.0L OHV older than 2000 does not have a knock sensor.

 

So my 03 is a flex fuel, is it safe to run 85 in it?

 

No. Even with a knock sensor, it only takes effect after a knock has already occurred, and even if it doesn't knock, the added heat still takes it toll on the valves, seats, and other components, and you will still get a decrease in performance and economy. Why are you even asking such a question? Do you not have an owners manual? What does it say on the subject? The decrease in economy is a greater cost that the few cents you save per gallon even if it didn't cause engine damage.

What your flex fuel does is let you run E85 (not to be confused with 85 octane), which is a blend of 85% ethanol and 15% gasoline. Its octane rating is about 105 - 110, obviously much higher than 85 octane gasoline. so if anything, flex fuel vehicles are designed to run on higher octane fuels, not lower.