People with gas mileage issues

[PowerJrod]

Ram and others allow the 87 because the octane sensors work properly and adjust timing based on what you use. Thus it is acceptable and will not void any warranty claims.

What does suffer is peak horsepower/tq as the maximum is based on the higher recommended octane of 89.

Thus 87 will see a slight drop and anything above 89 will not see anything better as the computer is not programmed to advance the timing past 89 octane readings.

For the vase majority of drivers they would never know the difference.

For me the Sams Club/Costco premium is the same price as 89 at regular stations or cheaper, so I typically mix the 87 and 93 between fill ups to average 89 or more....just because that is my personal preference.

Where you can typically see a large change is turbo motor vehicles. Usually around a 20-30 HP delta between 87-91 which should be noticeable.

That does make sense...no argument here. However the thing that made me scratch my head is when the manual states that 87 is acceptable...after that it says that it's normal to hear a slight knocking sound. That tells me it's not a good idea to use 87 continuously just for that reason alone. Knocking over time WILL cause engine damage eventually....might take a few years but it will happen. It's already been proven. But the way you go about filling is a good idea since you're blending high and low octane. Sounds like you end up averaging closer to 90 octane actually.

 

[Timeless]

That does make sense...no argument here. However the thing that made me scratch my head is when the manual states that 87 is acceptable...after that it says that it's normal to hear a slight knocking sound. That tells me it's not a good idea to use 87 continuously just for that reason alone. Knocking over time WILL cause engine damage eventually....might take a few years but it will happen. It's already been proven. But the way you go about filling is a good idea since you're blending high and low octane. Sounds like you end up averaging closer to 90 octane actually.

I do not think your version of knocking is what we people that have been driving a while is the same as it was 30+ years ago. So many horror stories of knock and engine failures I believe have skewed your judgement.

Today's engines 'knock' very often and manufacturers consider it normal. Hook up an OBDII logging tool and you will see for yourself.

That being said, I do blend the fuels to get 89 or higher.

 

[PowerJrod]

I do not think your version of knocking is what we people that have been driving a while is the same as it was 30+ years ago. So many horror stories of knock and engine failures I believe have skewed your judgement.

Today's engines 'knock' very often and manufacturers consider it normal. Hook up an OBDII logging tool and you will see for yourself.

That being said, I do blend the fuels to get 89 or higher.

I'm pretty sure I don't know anyone that actually works on their own vehicles who would say driving down the road with the engine knocking is totally fine lol. But at the end of the day...here's the question...why risk it? I've never had a engine knock...but I know at least 3 people off the top of my head who have had engine knock and had engine problems. (This was within the last 10 years)

 

[BowDown]

I'm pretty sure I don't know anyone that actually works on their own vehicles who would say driving down the road with the engine knocking is totally fine lol. But at the end of the day...here's the question...why risk it? I've never had a engine knock...but I know at least 3 people off the top of my head who have had engine knock and had engine problems. (This was within the last 10 years)

What he's probably referring to is piston slap on cold starts and while I agree that its not fine, many manufacturers have said that its normal.
What the noise is is the pistons rocking slightly in the bores when cold do to the use of hyperutectic piston materials (high silicon content pistons). These type of pistons contract or shrink when cold and expand to fill the bores when at operating temperature.

This cold start piston slap is what manufacturers call normal. Prolonged knocking past warmup isn't normal and at the point that knocking noises are heard while driving at operating temps is a problem.
Octane knock is actually pinging which is damaging the pistons and the chambers. Once you hear actual knocking and not pinging, you've got permanent damage, cracked or broken piston or an elongated journal on the rods big end.

 

[PowerJrod]

What he's probably referring to is piston slap on cold starts and while I agree that its not fine, many manufacturers have said that its normal.
What the noise is is the pistons rocking slightly in the bores when cold do to the use of hyperutectic piston materials (high silicon content pistons). These type of pistons contract or shrink when cold and expand to fill the bores when at operating temperature.

This cold start piston slap is what manufacturers call normal. Prolonged knocking past warmup isn't normal and at the point that knocking noises are heard while driving at operating temps is a problem.
Octane knock is actually pinging which is damaging the pistons and the chambers. Once you hear actual knocking and not pinging, you've got permanent damage, cracked or broken piston or an elongated journal on the rods big end.

That would make more sense for sure being a cold crank startup. But I was referring to the slight knocking while at operating temps. The manual doesnt say anything about slight knocking only at a cold startups though...idk lol.

 

[BowDown]

That would make more sense for sure being a cold crank startup. But I was referring to the slight knocking while at operating temps. The manual doesnt say anything about slight knocking only at a cold startups though...idk lol.

Slight knock after things are up to temp is a broken engine, period

 

[PowerJrod]

Slight knock after things are up to temp is a broken engine, period

That's what I was saying too...bad news. And that's why I was saying not worth the $0.20 per gallon savings lol

 

[Timeless]

I'm pretty sure I don't know anyone that actually works on their own vehicles who would say driving down the road with the engine knocking is totally fine lol. But at the end of the day...here's the question...why risk it? I've never had a engine knock...but I know at least 3 people off the top of my head who have had engine knock and had engine problems. (This was within the last 10 years)

I don't think you can definitely know this without logging your truck over extended time frames.

 

[PowerJrod]

I don't think you can definitely know this without logging your truck over extended time frames.

We're taking about audible engine knock...meaning you can hear it while driving at operating temps. And yes...you can hear it. Heard it on my coworkers when he was driving it...after almost a year of him using 87/low quality gas.

 

[Timeless]

We're taking about audible engine knock...meaning you can hear it while driving at operating temps. And yes...you can hear it. Heard it on my coworkers when he was driving it...after almost a year of him using 87/low quality gas.

Whether audible or not it seems you in particular would be worried....

 

[PowerJrod]

Whether audible or not it seems you in particular would be worried....

Interesting response....
Is there a question in there somewhere or a factual statement of any kind?????
Who in the hell wouldn't be worried???? Lmao. Smh.

 

[Timeless]

Interesting response....
Is there a question in there somewhere or a factual statement of any kind?????
Who in the hell wouldn't be worried???? Lmao. Smh.

Was basically pointing out how worried you are in regards to knocking...but somehow only if you can hear it.

A vast majority of knocking happens and you do not hear it and was suggesting you log it.

If you are not worried just ignore my post.

 

[PowerJrod]

Was basically pointing out how worried you are in regards to knocking...but somehow only if you can hear it.

A vast majority of knocking happens and you do not hear it and was suggesting you log it.

If you are not worried just ignore my post.

You would hear engine knocking if it was due to low octane fuel....it would be caused by premature fuel detonation. In fact...most engine knocking from other causes ARE audible. So I fail to understand your post... whether I'm worried or not.

 

[jmr]

From the manual 89 is recommended 87 acceptable but may result in light knock.
The engine has a 10.5:1 compression ratio so use 89 octane as RAM suggests.

 

[PowerJrod]

From the manual 89 is recommended 87 acceptable but may result in light knock.
The engine has a 10.5:1 compression ratio so use 89 octane as RAM suggests.

View attachment 66505

Exactly! Thank you

 

[BlueBillet]

All of you must live on flat lands and drive only highway. I drive mostly city (NJ will lots of hills) and a little highway. I average 10. that's right 10. The windows sticker that says 17 city is total BS. LOL
I may have a heavy foot and do enjoy the sound of the exhaust but really 10. Was expecting more

I get around 12 with similar setup on my Laramie 4x4. running 33"x12.5x20 no lift and borla atak exhaust. when I first bought the truck stock I was getting 14 if I take it very easy but I live the sound. Honestly think there is an issue with the fuel system how everyone is talking on here

 

[RRSBighorn]

I get average fuel mileage (which I consider decent) of about 18mpg mixed driving, and 20-22 on highway on longer trips. Pulling trailer, this thing sucks down the fuel fast, depending on conditions and grade.

I was reading the last few pages (not the whole thread) and was glad to see that someone finally explained the difference of how new computer controlled vehicles with knock sensors work, which is why you can run 87 octane.
I run 87 octane using top tier fuels when I'm doing normal day to day driving with no load except me. I agree if you can buy fuel with out ethanol, your better off, but I haven't found any place in the area since we're surrounded by cornfields.
I live in the Chicago area, and it doesn't get past the 90's daily in the summer. If I lived somewhere that was 90-100F most of the time, or pulling heavy loads all the time, I probably would use higher octane, assuming I'd hear engine pinging. I don't hear any engine pinging because the computer is adjusting the timing as said earlier. I do use 89 or higher when I'm pulling my travel trailer that weighs about 7k. Ram wouldn't be telling you that running 87 octane was acceptable if they thought it would cause damage, thus potentially more warranty work, there would be to many legal ramifications. I can tell that running 89 instead of 87, there is a noticeable in performance, so if getting from stop light to stop light quickly is your thing, than it may be worth the extra money for the 89 octane.

 

[ccokeman]

2019 5.7 equipped Quad cab 4x4 3.21 gears.
Combined city/highway I am consistently at between 18 and 19 MPG hand calculated. Highway only trips I can net out 21.5 to 22.3 MPG. The truck currently has 45K on the odometer. I use 89 octane almost exclusively. I do notice that average MPG does drop when using 87 octane and gets slightly better using ethanol free fuel. This is not using "Top Tier" fuel. Highway cruise speeds are between 75 and 80MPH. The only mods to the truck are a K&N drop in filter and cat back exhaust. I do not drive gently but sensibly based on the traffic I encounter. Drafting a tractor trailer at 65MPH does wonders for MPG. The best I ever got out of my 2004 5.7 3.92 geared truck was 22MPG by drafting a tractor trailer for 200 miles. The realistic average with that truck was 16 to 17 MPG at 75 MPH. This one delivers better fuel consumption results.
Just my experience with this truck!

 

[Wsmith]

The manual doesnt state that 89 is recommended for the 5.7??? You might want to recheck that lol. 87 Acceptable for how long? (That's a rhetorical question) but I think you get my point. No sense in arguing.

If the word acceptable is in print, that's all she wrote, but before I go to court for this I will just scrap it and get a Toyota.

 

[PowerJrod]

If the word acceptable is in print, that's all she wrote, but before I go to court for this I will just scrap it and get a Toyota.

Good point. Probably nothing we'd have to worry about if we're using 89 or higher at least 50% of the time (in theory anyway). I really wanted a Tundra but Toyota needs to update their engine line up as well as their interior. Not worth $45-$50k right now IMO.