87 to 89 to 93

opsbear7 · June 4, 2006

I was just reading in someone elses thread about MPG based on different octane levels. I dont really want to get to far into that arguement, but rather i am curious about the performance increase and wether it will do any damage to anything if i use 87 90% of the time and then everyonce and a while when i feel i want some extra get up and go or just some stupid reason i fill up on 93. Will this do any damage to any parts of my engine. I know it is going to burn hotter, but is there anything else?

OUMike · June 4, 2006

87 octane fuel will not hurt your truck in any way. Your truck was not designed to run on higher octane fuel, therefore you gain virtually nothing from running high octane. Save the cash or buy a cold beverage and a hot dog at fillup.

snoman · June 4, 2006

I was just reading in someone elses thread about MPG based on different octane levels. I dont really want to get to far into that arguement, but rather i am curious about the performance increase and wether it will do any damage to anything if i use 87 90% of the time and then everyonce and a while when i feel i want some extra get up and go or just some stupid reason i fill up on 93. Will this do any damage to any parts of my engine. I know it is going to burn hotter, but is there anything else?

<{POST_SNAPBACK}>

93 will not hurt your engine. Actually 87 stands more chance of that because it is constantly on the edge of detination as your knock sensor and ECM struggle to control knock before you here it which gives you the false impression that 87 is enough. THis constant transparent retarding of spark to control knock though effect power and MPG negatively. Also running on the ragged edge of knock is hard on valves and seats and can shorten there lifespan in a engine that is working hard often (such as towing) because of the encrerase valve tempature this causes and when a engine starts to ping/knock even lightly below your hearing, it cause valves to vibrate in seats some a leak a bit and with time it will erode the seats when working hard.

snoman · June 4, 2006

87 octane fuel will not hurt your truck in any way. Your truck was not designed to run on higher octane fuel, therefore you gain virtually nothing from running high octane. Save the cash or buy a cold beverage and a hot dog at fillup.

<{POST_SNAPBACK}>

This is not correct, as there is a lot of misconceptions here. The only reason there is 87 in the owner manual and a knock sensor is because of the public affinity for cheapest possible gas because a engine with 9 to 1 CR or higher was not designed for 87, it was banaided with a knock sensor to limit consumer complaints and the stigma to sales of saying that it really needs more than 87. All EPA MPG tests are conducted using 93 octane, none of them do it using 87 but they never volunteer that info to you. (nor do they tell you that the EPA high test has a average speed of 48 MPH and never exceeds 59) You are not saving any cash at all and if you ran a few tanks of atleast 89 you will likely find it is cheaper to drive it on better gas. Even my wifes 4cyl Cheerke pickup up a few MPG in city driving in warmer months with better gas. The best it would do was upper teens in city urban driving to work. With 89 or better it does low 20's even using A/C.

Rammer · June 4, 2006

I've logged 2 stock trucks with 87 octane gas and both would show about 3 degrees of knock retard in the 1400-2000 RPM cells with a semi light load on the engine. Not all the cells in that range had knock, but enough for the PCM to pull the timing. These were 05 trucks. Running 89 octane in these two trucks should be enough to eliminate the KR the PCM was hearing. I never heard either one knock.

There are two timing table in the program. The High octane and the Low octane. The PCM will try to run off the high table. As knock is detected, the PCM "learns" the knock and starts to blend the high table with the low table until knock is gone. If no more knock is present, the PCM will move towards the high table again. The PCM will remove timing a lot faster than it will return timing. There is more to this, but this should give you an idea on how this works.

This is on the 99^ LS1 based PCM's.

snoman · June 4, 2006

I've logged 2 stock trucks with 87 octane gas and both would show about 3 degrees of knock retard in the 1400-2000 RPM cells with a semi light load on the engine. Not all the cells in that range had knock, but enough for the PCM to pull the timing. These were 05 trucks. Running 89 octane in these two trucks should be enough to eliminate the KR the PCM was hearing. I never heard either one knock.

There are two timing table in the program. The High octane and the Low octane. The PCM will try to run off the high table. As knock is detected, the PCM "learns" the knock and starts to blend the high table with the low table until knock is gone. If no more knock is present, the PCM will move towards the high table again. The PCM will remove timing a lot faster than it will return timing. There is more to this, but this should give you an idea on how this works.

This is on the 99^ LS1 based PCM's.

<{POST_SNAPBACK}>

When I monitored the ECM on a 06 with 87 and 93, there was a 4 to 6 degree difference in average timing advance and 4 to 5 more degrees of advance WOT with 93 and the truck ran like a completely diffent animal too with 93 and it even surprized me how well it wond out and pulled with 93 in it vs 87.

opsbear7 · June 4, 2006

so it sounds like to me that there is no benefit of filling up with 93, but filling with 87 is not to great either. I think i will stick with 89 then and call it a day. That way i am getting good performance and not risking knock issues. Thanks for your help guys!

snoman · June 4, 2006

so it sounds like to me that there is no benefit of filling up with 93, but filling with 87 is not to great either. I think i will stick with 89 then and call it a day. That way i am getting good performance and not risking knock issues. Thanks for your help guys!

<{POST_SNAPBACK}>

If you are average driver 89 will do you but if you drive in hot weather and tow too, 93 will help because a engines octane requirement goes up with tempature and load as it is not constant.

overlord1 · June 4, 2006

Snoman & others,

I was going to ask a similar question. I have an 06 Z71 with the 5.3L engine and tow package (and the crappy 3.42 gears ). I have been running nothing but 87 octane Exxon fuel since new (3500 miles currently on the odo). It is hot and humid here in the South and I sometimes tow a landscaping trailer. Will using a higher octane fuel (say 89 octane) have any effects (more/less/the same) on the amount of carbon buildup in the fuel system? One always hears about how it is a waste of money to use anything other than 87 octane fuel unless you have a "high performance engine" or your owners manual specifically calls for it. I have become really intrigued by what you and a VERY FEW others have said, that is go with at least 89 octane or even 93 for the best performance and MPG. Thanks.

Ed

OUMike · June 5, 2006

All I know is I've got a 94' with 198,850 and zero major engine trouble for its entire life. I get 16-20 mpg and run strickly 87.

larry arizona · June 5, 2006

Makes me wonder if the advertised HP and Torque ratings from the maufacturer is done with 87 or 93.

I am currently testing a wait4me econo tune and the claim is better MPG with higher octane.

Gained 0.6MPG with 87 and the tune. Currently running 93 and we will see what happens.

LA

snoman · June 5, 2006

Snoman & others,
I was going to ask a similar question. I have an 06 Z71 with the 5.3L engine and tow package (and the crappy 3.42 gears ). I have been running nothing but 87 octane Exxon fuel since new (3500 miles currently on the odo). It is hot and humid here in the South and I sometimes tow a landscaping trailer. Will using a higher octane fuel (say 89 octane) have any effects (more/less/the same) on the amount of carbon buildup in the fuel system? One always hears about how it is a waste of money to use anything other than 87 octane fuel unless you have a "high performance engine" or your owners manual specifically calls for it. I have become really intrigued by what you and a VERY FEW others have said, that is go with at least 89 octane or even 93 for the best performance and MPG. Thanks.

Ed

<{POST_SNAPBACK}>

Not sure when you are taking about with "carbon" build up in fuel system. The only reason that your manual says 87 is for sales purposes, not because it is the best fuel for it. The ECM knock control does a good job of fooling into thinking 87 is enoingh because your engine will never knock if it works properly but you will never know what performance you are missing untill you run a few tanks of better gas. If you towing in hot weather with 87, rest assured that you are lossing power and MPG with it. (Detriot uses 93 when they run EPA test and that should tell you something too.) 87 octane was "designed" for engine running about 8 to 1 compression when the grade came out.

jaslo · June 5, 2006

Makes me wonder if the advertised HP and Torque ratings from the maufacturer is done with 87 or 93.

I am currently testing a wait4me econo tune and the claim is better MPG with higher octane.

Gained 0.6MPG with 87 and the tune. Currently running 93 and we will see what happens.

LA

<{POST_SNAPBACK}>

Let me know what you get, because I have the economy tune also. I get around 18 with 87 and I used 91 and got a little worse. Best I gotten was 18.6. Jesse also told me that his tunes can run on 87-93 octane. Did he tell you that also?

larry arizona · June 5, 2006

Jesse told me to expect 1-2MPG between 87-89 octane and 2-4 with 91-93 octane. He said the PCM will adjust for the octane and can be used with 87-93.

How much of a gain did you see with the econo tune? I went from 16.5 to 17.1 with 87 octane on my first tank with the econo tune.

Have not stepped on it hard to see if the seat of the pants feel is better with his tune.

He also changed my tow/haul mode to be a better towing mode? Not sure exactly what to expect from that change?

I am only 80 miles into my first tank of 93 octane so it will be about 2 weeks before I clear this full tank trial of 93.

I will post results. 100% city driving and I drive the same route every day during this test so it is accurate.

dewfpo · June 5, 2006

I was just reading in someone elses thread about MPG based on different octane levels. I dont really want to get to far into that arguement, but rather i am curious about the performance increase and wether it will do any damage to anything if i use 87 90% of the time and then everyonce and a while when i feel i want some extra get up and go or just some stupid reason i fill up on 93. Will this do any damage to any parts of my engine. I know it is going to burn hotter, but is there anything else?

<{POST_SNAPBACK}>

I'm not sure what you mean by burn "hotter"

Premium unleaded doesn't have any more btu's in it then reg. or mid-grade. Maybe a little less because of a higher percentage of additives.

If you mean the engine will run hotter because you can advance the timing more when using PUL, then that might be so but you wouldn't notice it on the temp gauge.

DEWFPO