Better MPG on 93?

StevenStarke · January 17, 2019

1 hour ago, gothp28 said:

Truck looks great! Did you have to have any rubbing? Lift? Offset? I take delivery of mine in 2 weeks and would like to purchase rims and tires. Sorry for all the questions but I appreciate any answers that you give.

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RC level only. Wheels are 20x10 -24 offset. Tires are Toyo AT2 295/65/20. Yes they rubbed and I trimmed the mud flaps and fenderwell. It still rubs on full lock but it’s mostly manageable. My only concern now is the fact that there is a square hole in the fender well. It’s right where Ice builds up during snow storms. So I have to Figure how I’m going to cover that up before the next storm. I may have to do that NorCal mod.

eppieguy · January 17, 2019

I'd go to a local vinyl shop and have something either cut in black or the matching white and make a trim piece that will look factory and will also serve as chip protection, wrap it to the inside of the fender, nobody except you will know it's not OEM if you do it right.

StevenStarke · January 17, 2019

48 minutes ago, eppieguy said:

I'd go to a local vinyl shop and have something either cut in black or the matching white and make a trim piece that will look factory and will also serve as chip protection, wrap it to the inside of the fender, nobody except you will know it's not OEM if you do it right.

The problem with that is I turn it too much and it catches on the tire, it will rip off. I need something harder.

Sierra Dan · January 17, 2019

We have a few stations here in the KC area that sell 93 octane that is Ethanol Free.

eppieguy · January 17, 2019

2 hours ago, StevenStarke said:

The problem with that is I turn it too much and it catches on the tire, it will rip off. I need something harder.

Well, If your tire is actually hitting the metal on the fender you've got much bigger issue than a hole to cover. The vinyl should only be on the metal fender, if your tire is hitting the actual fender you're screwed the first time you driver up a driveway apron or little curbing and rip the fender apart.

Daverado · January 17, 2019

3 hours ago, Texas Daddy said:

Blackbear posted an article years ago about the ls truck engines needing higher octane with their increased compression ratios. The gen 4 5.3 likes 89 better than 87, and you can tell a difference...

Yeah, it's a wording challenge. With knock sensors hardly any regular car engine "requires" premium gas. Even my wifes 1.8T VW doesn't "require" premium gas, they don't even recommend it in the manual IIRC. Crazy.

Many modern cars can certainly benefit from it and will absolutely take advantage of it if given the chance. Most drivers won't notice or care though, it's the drivers that don't "require" it.

KA0S · January 17, 2019

It's "recommended" for the 6.2. NOT "required". There's a big difference.

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ftwhite · January 17, 2019

Here is the wording in the manual:

For the 6.2L engine, premium unleaded gasoline meeting ASTM specification D4814 with a posted octane rating of 93 is highly recommended for best performance and fuel economy. Unleaded gasoline with an octane rated as low as 87 can be used. Using unleaded gasoline rated below 93 octane, however, will lead to reduced acceleration and fuel economy. If knocking occurs, use a gasoline rated at 93 octane as soon as possible, otherwise, the engine could be damaged. If heavy knocking is heard when using gasoline with a 93 octane rating, the engine needs service.

Loco-diablo · January 18, 2019

I’ve been running 89 in my 2017 5.3 since day one.. not sure if it makes a difference in mpg, but it feels like it runs better than 87. The difference here in Massachusetts is about .20/25 per gallon.

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Sierra Dan · January 18, 2019

15 hours ago, ftwhite said:

Using unleaded gasoline rated below 93 octane, however, will lead to reduced acceleration and fuel economy.

The manual is basically stating to use 93 or else!

amxguy1970 · January 18, 2019

1 hour ago, Sierra Dan said:

The manual is basically stating to use 93 or else!

No it doesn't "Unleaded gasoline with an octane rated as low as 87 can be used." Hence the word recommended...

87 works just fine except in more extreme circumstances and heat/loads. Been running 87 in our 6.2 since new most of the time, only notice a little over 1 mpg difference. Acceleration difference isn't noticeable nor is how smooth it is, though it is rarely run full throttle. Most of the time people say it is some huge difference between the two is a placebo effect, they can't notice a 10-15 hp swing or the smoothness difference in modern engines.

The 6.2 is tuned for premium where as the 5.3 isn't, so the 5.3 isn't going to gain much if anything running premium other than a peace of mind or the earlier mentioned placebo effect. Now E85, that is a different story.

Tyler

KA0S · January 18, 2019

No it doesn't "Unleaded gasoline with an octane rated as low as 87 can be used." Hence the word recommended...

87 works just fine except in more extreme circumstances and heat/loads. Been running 87 in our 6.2 since new most of the time, only notice a little over 1 mpg difference. Acceleration difference isn't noticeable nor is how smooth it is, though it is rarely run full throttle. Most of the time people say it is some huge difference between the two is a placebo effect, they can't notice a 10-15 hp swing or the smoothness difference in modern engines.

The 6.2 is tuned for premium where as the 5.3 isn't, so the 5.3 isn't going to gain much if anything running premium other than a peace of mind or the earlier mentioned placebo effect. Now E85, that is a different story.

Tyler

I run 91-94 in mine, but I'm fairly certain that the first tank from the dealer was Regular.

There's only a 5 cent/litre difference from 91 to 94, so I'll pay that any day.

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L86 All Terrain · January 21, 2019

On ‎2019‎-‎01‎-‎17 at 10:36 AM, StevenStarke said:

RC level only. Wheels are 20x10 -24 offset. Tires are Toyo AT2 295/65/20. Yes they rubbed and I trimmed the mud flaps and fenderwell. It still rubs on full lock but it’s mostly manageable. My only concern now is the fact that there is a square hole in the fender well. It’s right where Ice builds up during snow storms. So I have to Figure how I’m going to cover that up before the next storm. I may have to do that NorCal mod.

It is your wheel offset that is beating you up. You need a offset around +18mm to clear a large tire with no rub, even with the larger wheel wells on the new T1. I would try trading the wheels for some with a more neutral offset if you are deeply concerned/don't want to cut things, or have a tire shop mount a 305/55R20 and see if that helps. My K2 fits a 33x12.5 which is wider than both, but not as tall as your tire also that is on a +23mm offset, not a -24.

StevenStarke · January 21, 2019

2 hours ago, L86 All Terrain said:

It is your wheel offset that is beating you up. You need a offset around +18mm to clear a large tire with no rub, even with the larger wheel wells on the new T1. I would try trading the wheels for some with a more neutral offset if you are deeply concerned/don't want to cut things, or have a tire shop mount a 305/55R20 and see if that helps. My K2 fits a 33x12.5 which is wider than both, but not as tall as your tire also that is on a +23mm offset, not a -24.

My tires rub on the bracket that’s behind the rear of the fenderwell. 305/55/20’s don’t work either. My friend already tried those with a level.

And An -18 offset will not clear if a -24 won’t. Sinking the wheel 6 more mm in isn’t going to make it clear.

Also. I considered the Norcal mod but it wouldn’t work on this truck. Well, that’s not where my truck is rubbing so it wouldn’t matter. There is a bracket bolted to the body behind the rear fenderwell that sticks out towards the tire about 2-2.5”. If the bracket didn’t do that, the well could be pushed in more and the tire would prob clear on full lock. I may try to have something custom made.

Wintersun · January 22, 2019

The Octane rating is as was mentioned a measure of pre-ignition or knock resistance and it is not a linear rating. If you take 10 gallons of 89 octane rated gasoline and mix it with 2 gallons of 100 octane fuel the result is going to be in the 93 octane range. People assume that if you mix 5 gallons of 93 octane and 5 gallons of 100 octane gas the result is a 96 octane fuel and it does not work that way with respect to pre-ignition.

With my coupe that was designed for premium my mpg would drop by about 7% if I used 89 octane gas in the tank. The 93 octane gas costs about 10% more so there is no gain either way. So I used premium fuel in the coupe.

On the other hand my 2018 Traverse has a V-6 engine designed to run on 87 octane gasoline and going with higher octane gas would be a complete waste of money in every respect. Every 50,000 miles I do plan to invest in fuel injector cleaner and add it to the tank and that is a worthwhile investment.