Issues running fuel other than premium in the RT?

[NancysToy]

Dilema time again. We just topped $4.43 for 90 (highest available) octane in AK. I'm still saying it will be $5.00 by Memorial Day. I have felt that performance was not as good on 87 or 88 (our mid-grade) and that the mileage was a little less. I filled up with 88 yesterday--just because I did not want to get shafted again. I know when I start heading out and about on the weekends that I am going to encounter $5.00 and up when I get away from Anchorage metro area. opcorn:

We're ahead of you. I paid $4.52 for premium today.

 

[Bob Denman]

Gee... I tanked up the other day at $4.35 per gallon. Maybe I should feel lucky?!? :shocked:
(Valero station in Neversink, NY)

 

[rogerb]

Right now Conneticut is the highest in the New England area and N. H. & N. Y. have some of the best prices. Maine isn't real bad but you get ethanol.

 

[cjackg]

I have used a lot of non-ethanol gas as it is available closeby.

I have also used ethanol regular, mid-grade, and premium in my RT and I have to say I cant see much difference at all in how the RT performs, or the mileage. Mid-grade is probably the best bet, non-ethanol if you can get it.

 

[dancogan]

Wow! Diesel was priced below regular at the BP station in town today. That's a switch. Also a good sign as we're trading in a motorhome with a Ford V-10 for a smaller one with a small diesel engine.

 

[SpyderAnn01]

Wow! Diesel was priced below regular at the BP station in town today. That's a switch. Also a good sign as we're trading in a motorhome with a Ford V-10 for a smaller one with a small diesel engine.

I bought a diesel car in late 2008 when the price of diesel was about the same as regular gas. Shortly after that it went up to the same price as premium. I got rid of the car in November and now the price will probably go lower than regular! Timing is everything.

 

[challman]

I've always run 93 octane in mine... the difference in the cost of re-fueling works out to about a dollar and my Missus can tell you that nobody can waste a dollar quicker than me! :lecturef_smilie: I don't imagine that running 87 could in any way harm the engine; it just wouldn't be making peak horsepower and torque numbers as the 'puter compensates for the lower octane swill... :shocked:

Actually

Octane rating of gas measures its ability to resist self combustion under high pressure. If you have a High compression piston setup, you need higher octane gas. If you don't use High octane, it has a tendency to combust before the plug fires which is more before top dead center than is intended. This can cause what is called pre-detonation. or Pinging. This is not always audible but can cause overheating, valve and bearing damage and a reduction if fuel economy
. USE at least the octane specified for your engine. Using higher won't hurt since high octane gas has the same explosive characteristics as well as equal amounts of energy.

 

[SpyderGirl]

Actually

Octane rating of gas measures its ability to resist self combustion under high pressure. If you have a High compression piston setup, you need higher octane gas. If you don't use High octane, it has a tendency to combust before the plug fires which is more before top dead center than is intended. This can cause what is called pre-detonation. or Pinging. This is not always audible but can cause overheating, valve and bearing damage and a reduction if fuel economy
. USE at least the octane specified for your engine. Using higher won't hurt since high octane gas has the same explosive characteristics as well as equal amounts of energy.

I am very familiar with pre-detonation and the effects it has on a motor (I took an auto mechanics class a few years ago). I have always used 87 in my RS, of course now I am thinking that I should start using at least mid-grade and probably will do the same in the RT (whenever we get it).

Thank you all for the input.

 

[Bob Denman]

Octane rating of gas measures its ability to resist self combustion under high pressure. If you have a High compression piston setup, you need higher octane gas. If you don't use High octane, it has a tendency to combust before the plug fires which is more before top dead center than is intended. This can cause what is called pre-detonation. or Pinging. This is not always audible but can cause overheating, valve and bearing damage and a reduction if fuel economy
. USE at least the octane specified for your engine. Using higher won't hurt since high octane gas has the same explosive characteristics as well as equal amounts of energy.

The 991s are a bit over 12:1...:shocked:
I do think that the electronics can be brought into play to prevent engine damage. If the timing is retarded; won't that help out? :dontknow:
Believe me... no expert hiding here!

 

[challman]

The 991s are a bit over 12:1...:shocked:
I do think that the electronics can be brought into play to prevent engine damage. If the timing is retarded; won't that help out? :dontknow:
Believe me... no expert hiding here!

Sort of. There is actually a point where the low octane doesn't cause pre-detonation (ignition before the spark) but instead cause detonation. Most people think that there is an explosion in the cylinder when the spark goes off. This is more or less true but the actual truth is that you want a controlled burn and expansion. If the fuel actually explodes, that is called detonation. Higher octane also resists this. You can help detonation by causing the spark to be later. This helps minimize the wear and tare on the engine but still isn't optimal. So for condition A Pre-detonation.. Changing the timing will not help.. For condition B changing the timing can help but you cannot get an optimal burn and therefore although you minimize (not stop) additional engine wear and fuel economy, you just can't get as good an operating engine by modifying engine timing to compensate for for to low an octane fuel.

Incidentally.. This is what the Knock sensor does. It senses when the engine is experiencing either Pri-detination or detonation, and attempts to adjust timing to compensate.

Cole

 

[Bob Denman]

Aha! :thumbup: Nice explanation! :clap: