What gas are you running in your 19 5.7's?

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star_deceiver

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Cold, winter, snow, 4wd... last tank was around 13.5mpg on the usual 89. City/Highway fast, slow... red light red light freeway 80mph merge off to red lights... get out of my way...

Never used 87 but I alternate usually between Mobil station 89 and Costco 91, whichever is cheaper.

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brian42

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Dealer says use 87....full tank when picked up.
I got a full tank when I bought mine too and it was probably 87 octane. It's cheaper to fill it with 87 so either they just don't know (or care) or by saying that they can give you a tank of 87 instead of 89.

Dealer says use 87....full tank when picked up.
The dealership is right and wrong.

Not sure which book you are referring to. There is the Essentials Information Guide that you get in the glovebox when you bought the truck then there's the Owner's Manual that you have to get on-line that's 23MB and 645 pages long. I don't think the Guide in your glovebox talks about filling up or fuel requirements.

In the Owner's manual it says you can use 87-89 octane just fine but that the "plus" (89 octane) is recommended. Here's the excerpt from the Owner's Manual (page 520) about gas for the 5.7L:

5.7L Engine
Do not use E-85 flex fuel or ethanol blends greater than 15% in this engine. This engine is designed to meet all emissions regulations and provide satisfactory fuel economy and performance when using high-quality unleaded gasoline having an octane range of 87 to 89 as specified by the (R+M)/2 method. The use of 89 octane “Plus” gasoline is recommended for optimum performance and fuel economy.

While operating on gasoline with an octane number of 87, hearing a light knocking sound from the engine is not a cause for concern. However, if the engine is heard making a heavy knocking sound, see your dealer immediately. Use of gasoline with an octane number lower than 87 can cause engine failure and may void or not be covered by the New Vehicle
Limited Warranty. Poor quality gasoline can cause problems such as hard starting, stalling, and hesitations. If you experience these symptoms, try another brand of gasoline before considering service for the vehicle.

Reformulated Gasoline
Many areas of the country require the use of cleaner burning gasoline referred to as “Reformulated Gasoline”. Reformulated gasoline contains oxygenates and are specifically blended to reduce vehicle emissions and improve air quality. The use of reformulated gasoline is recommended. Properly blended reformulated gasoline will provide improved performance and durability of engine and fuel system components.

Materials Added To Fuel
Besides using unleaded gasoline with the proper octane rating, gasolines that contain detergents, corrosion and stability additives are recommended. Using gasolines that have these additives will help improve fuel economy, reduce emissions, and maintain vehicle performance. Designated TOP TIER Detergent Gasoline contains a higher level of detergents to further aide in minimizing engine and fuel system deposits. When available, the usage of TOP TIER Detergent gasoline i s recommended. Visit www.toptiergas.com for a list of TOP TIER Detergent Gasoline Retailers.

Indiscriminate use of fuel system cleaning agents should be avoided. Many of these materials intended for gum and varnish removal may contain active solvents or similar ingredients. These can harm fuel system gasket and diaphragm materials.
 
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Jerrybob

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Thanks Brian....I downloaded the manual....glad I have it...thanks.
 

turkeybird56

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DELETE:

Another member posted manual info ref using 89 Octane
 

magic280z

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I have tracked my fuel records with acar most of the time I had my 4th gen. Pretty much avg 17 mpg and according to the records I got slightly less mpg with 89 than 87. Most of that was 25 mile commute 15 interstate at 78mph. The other 10 at 45 with mild traffic and lights. The last 1 mile takes 5 minutes somtimes.

That was a 2016 Express quad cab 5.7 3.21 8 spd.

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Jrod

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87 octane, 56k miles, been driving the speed limit everywhere lately, 17 mpg. I was averaging 14mpg speeding around everywhere.
 

ScLeCo

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9 mpg around town.
 
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