Any benefit to running anything above regular (87 octane) in 4.8L V8?...

[Dawg82]

My 20-year-old "lake house tow vehicle" has been conscripted into daily duty once again. Just curious if anyone has seen any performance or mileage benefit from using midgrade or premium in the 4.8 ?

 

[swathdiver]

My 20-year-old "lake house tow vehicle" has been conscripted into daily duty once again. Just curious if anyone has seen any performance or mileage benefit from using midgrade or premium in the 4.8 ?

Excepting direct injected engines, I have ALWAYS seen a mileage and performance benefit from running higher octane fuel compared with lower octane fuel. There's even a difference in performance between brands.

You'll have to decide what's more important to you, cost per mile or running quality fuel versus discount swill through your motor or some other reason. I reckon that since nowadays Top Tier fuels put the additives in the lower grades, you could still run 87 from say Chevron and see a benefit over convenience store no-name gas.

Just have to test it out and see.

 

[nonickatall]

My 20-year-old "lake house tow vehicle" has been conscripted into daily duty once again. Just curious if anyone has seen any performance or mileage benefit from using midgrade or premium in the 4.8 ?

I would rather invest in good oil and maintenance, than in "better" fuel.
But that is only my my humble view...

 

[BG1988]

Excepting direct injected engines, I have ALWAYS seen a mileage and performance benefit from running higher octane fuel compared with lower octane fuel. There's even a difference in performance between brands.

You'll have to decide what's more important to you, cost per mile or running quality fuel versus discount swill through your motor or some other reason. I reckon that since nowadays Top Tier fuels put the additives in the lower grades, you could still run 87 from say Chevron and see a benefit over convenience store no-name gas.

Just have to test it out and see.

gas station matters the most i fill a the local truck stop called pilot.. they also have free air and can pump the tires fairly quickly

 

[nonickatall]

Do they use proper Winter and Summer Air...?

 

[RST Dana]

Since there are no additional fuel additives once the fuel leaves the tank farm, most brands will have the EXACT same liquid at the pump no matter what the brand. The only exception will be a few areas which have multiple tank farms and one caters to the low end resellers. So Exxon or 7/11, same product.

 

[Marky Dissod]

I would rather invest in good oil and maintenance, than in "better" fuel.

Better fuel IS better maintenance.
Higher octane fuel leaves less post-combustion deposits behind.

However, since there is no way to objectively measure how much less carbon is being left behind, there is no way to quantify the benefit of using higher octane fuel.
It follows that no one can objectively determine to what extent anyone is being overcharged for higher octane petrol, even where the cheapest higher octane fuel is to be found.

Yes, this assumes no meaningful difference between fuels from different brands.

 

[drdave81]

If your engine has a factory tune on the ECM, running a higher grade fuel will not change anything. Your engine/ECM are tuned for 87 octane and to handle any detonation based on that. Changing fuel without changing the tune doesn't do any good because the ECM doesn't know it has any different fuel in it. So it will still adjust the timing/fuel output/etc etc etc based on what it knows and is tuned for. People boasting mileage changes based on running premium vs regular is usually nothing more than a placebo effect or subconsciously driving differently due to that fuel change and hoping for a mileage difference. I fully expect arguments to that, but it has been proven that running different octanes than what you're tuned for doesn't give a benefit.

 

[Marky Dissod]

By the time the P01 / P59 pcms came into use, there have always been two different octane tables, low and high.
If the 4.8L had both tables written identically, then that would effectively be the same as having one table, which would make the above argument true.
Since 4.8L V8s are 'dumb', I've never bothered to look at them, so I frankly cannot speak of them.

That said, if there effectively is only one spark timing table that treats both fuels identically, the engine cannot fully utilize higher octane fuel; however that does not mean higher octane fuel itself behaves exactly the same as lower octane fuel.
Unfortunately, again, no objective way to know without proper testing to weed out subjective biases.

I do know that Gen3 & Gen4 5.3L & 6.0L V8s, as well as Gen4 6.2L V8s, have low and high octane tables that are written differently, and that those engines, with or without flex capability, use BOTH tables in tandem to determine how much timing to apply in any split second.

In other words, if you have a 5.3L or larger V8, and you plan on doing anything that could be construed as working or playing hard with your engine, it would be wise to use higher octane fuel if you can afford it.

 

[02slpSS]

By the time the P01 / P59 pcms came into use, there have always been two different octane tables, low and high.
If the 4.8L had both tables written identically, then that would effectively be the same as having one table, which would make the above argument true.
Since 4.8L V8s are 'dumb', I've never bothered to look at them, so I frankly cannot speak of them.

That said, if there effectively is only one spark timing table that treats both fuels identically, the engine cannot fully utilize higher octane fuel; however that does not mean higher octane fuel itself behaves exactly the same as lower octane fuel.
Unfortunately, again, no objective way to know without proper testing to weed out subjective biases.

I do know that Gen3 & Gen4 5.3L & 6.0L V8s, as well as Gen4 6.2L V8s, have low and high octane tables that are written differently, and that those engines, with or without flex capability, use BOTH tables in tandem to determine how much timing to apply in any split second.

In other words, if you have a 5.3L or larger V8, and you plan on doing anything that could be construed as working or playing hard with your engine, it would be wise to use higher octane fuel if you can afford it.

You are correct there just like every other Gen3 or Gen4 with a high and low octane table and actually they have more timing than a 5.3 or 6.0 due to the lack in down low torque there high octane timing table is somewhat similar to a stock 2002 camaro ls1

As far as what fuel to run I would personally would run 91 or 93 which ever is your highest octane in your area to keep your motor running at its full potential