Useless Information

[swathdiver]

Ok James... school me...

What is the purpose of a lower thermostat with a lower viscosity oil???

I have considered changing to a 0w20 or 0w30 oil as well and never gave a thought to changing the thermostat.

A 0w30, at operating temperature, would effectively be no different than the 5w30, at operating temperature, we are running now.

Also would we need to account for the thermostat change in the tune?

Would the ECU ever get out of open loop if it didn't "see" the engine was up to temperature?

Well Ken, I think the lower temperature combined with the 0W20 oil would allow the lighter oil to have a higher shear resistance, the ASTM D4683 standard. Many 0W20s are 2.7-2.9 while the 5W30s are 3.0-3.3 @ 302 degrees.

There's a lot for me to learn on this, my eyeballs are hurting from gathering all the oil specs and trying to learn what they mean!

I do not think it wise to lower the temperature to 160 like I did in the old days. As one of my racing mentor's used to tell me, "Heat Makes Horsepower". But if we lowered our engine temp about 7-10 degrees, that would keep the engine oil to around 212 at high speed and lower the trans a little more and the ECT too of course.

The tune could be changed to take advantage, especially the fan kick on speed lowered a corresponding amount.

Yes, too cold would be a problem and cause the motor to run rich and get worse mileage.

I've been following Grumpy Bear's posts over at GM-Trucks and how he has an average mpg of nearly 30 mpg with his V6 full size pickup. He's doing things along the lines as I used to years ago.

Just thinking of ways to tweak the mpgs and still have the cake.

Do you have any new highway mileage numbers on yours?

 

[kbuskill]

Well Ken, I think the lower temperature combined with the 0W20 oil would allow the lighter oil to have a higher shear resistance, the ASTM D4683 standard. Many 0W20s are 2.7-2.9 while the 5W30s are 3.0-3.3 @ 302 degrees.

There's a lot for me to learn on this, my eyeballs are hurting from gathering all the oil specs and trying to learn what they mean!

I do not think it wise to lower the temperature to 160 like I did in the old days. As one of my racing mentor's used to tell me, "Heat Makes Horsepower". But if we lowered our engine temp about 7-10 degrees, that would keep the engine oil to around 212 at high speed and lower the trans a little more and the ECT too of course.

The tune could be changed to take advantage, especially the fan kick on speed lowered a corresponding amount.

Yes, too cold would be a problem and cause the motor to run rich and get worse mileage.

I've been following Grumpy Bear's posts over at GM-Trucks and how he has an average mpg of nearly 30 mpg with his V6 full size pickup. He's doing things along the lines as I used to years ago.

Just thinking of ways to tweak the mpgs and still have the cake.

Do you have any new highway mileage numbers on yours?

Haven't really been anywhere lately... Been to busy running around to Dr's and physical therapists and surgeons.

 

[Tonyrodz]

Haven't really been anywhere lately... Been to busy running around to Dr's and physical therapists and surgeons.

That def sux! Feel better man.

 

[iamdub]

Aerodynamics play a role in the non-linear MPG curve. I'm sure you already know that the coefficient of drag increases in a square to the velocity. So, as speed increases, the drag does exponentially. What I suspect causes the "dip" in the curve may be areas of high and low pressures forming at various speeds which essentially alter the way the higher-velocity air flows over the vehicle, as if the vehicle changed it's shape. This is much how leaving a tailgate up versus down actually creates less drag because, at highway speeds, the bed fills with high pressure air which lets the higher-velocity air (lower pressure) skim over it like a bed cover. This effect varies with speed. So, my thoughts are that maybe at lower speeds, there isn't/aren't a pocket(s) of air so the hard shape of the vehicle determines the drag. Then, at higher speeds, a pocket/some pockets develop, reducing drag enough to overcompensate for the extra fuel consumed by the increased engine RPM. Then, at even higher speeds, the fuel needed balances and then overcomes even that drag efficiency.

 

[swathdiver]

Haven't really been anywhere lately... Been to busy running around to Dr's and physical therapists and surgeons.

Same here, that's most of my trips out of the house too! Progress being made or treading water?

 

[swathdiver]

Aerodynamics play a role in the non-linear MPG curve. I'm sure you already know that the coefficient of drag increases in a square to the velocity. So, as speed increases, the drag does exponentially. What I suspect causes the "dip" in the curve may be areas of high and low pressures forming at various speeds which essentially alter the way the higher-velocity air flows over the vehicle, as if the vehicle changed it's shape. This is much how leaving a tailgate up versus down actually creates less drag because, at highway speeds, the bed fills with high pressure air which lets the higher-velocity air (lower pressure) skim over it like a bed cover. This effect varies with speed. So, my thoughts are that maybe at lower speeds, there isn't/aren't a pocket(s) of air so the hard shape of the vehicle determines the drag. Then, at higher speeds, a pocket/some pockets develop, reducing drag enough to overcompensate for the extra fuel consumed by the increased engine RPM. Then, at even higher speeds, the fuel needed balances and then overcomes even that drag efficiency.

I reckon that's so but figured it would be more linear as speed increases. In addition, the truck on E85 dropped .8 mpg from 65 to 70 and .5 from 70 to 75. MPG were essentially the same at 60 and 65 mph. Now that E85 made more horsepower so it was able to maintain speed with less drop in mileage as the resistance increased. Now I need a wind tunnel to test this thing!

On the other hand, the mileage ratings seem to fall in line with those trucks with 3.08 gears. At 70 mph they're turning about 1500 rpms with 3.08 gears. Mine will turn about 1500 rpms at 65 mph. And if you were to turn 1500 rpms in top gear, that would be 54 mph! Does being shorter and lighter make that much difference? Not according to GMs fuel economy ratings for these trucks but real world should be different. I guess I could take a look at Fuelly and see what the short and long trucks are averaging.

 

[kbuskill]

Same here, that's most of my trips out of the house too! Progress being made or treading water?

Slowly but surely.

 

[swathdiver]

Ok, just got back from a trip to Fuelly and my trusty Excel spreadsheet.

The purpose of this post is to see averages of the types. These are the averages of the mileage that people post, so it is a combined city/highway rating.

5.3 Flex Fuel engines were chosen. 2007-2014. Tahoe, Yukon, Avalanche, Suburban, Yukon XL

There are many ways to figure averages and I did them. By year, model and short or long and by features.

So here's an example:

For the Tahoe/Yukon:

2007-2008 = 14.38 MPG (4-Speed Transmissions and Single Pattern Camshafts)
2009 = 14.65 MPG (6-Speed Transmissions and Single Pattern Camshafts)
2010-2014 = 14.54 MPG (6-Speed Transmissions and Dual Pattern Camshafts with VVT)

For the Avalanche/Suburban/Yukon XL

2007-2008 = 13.90 MPG (4-Speed Transmissions and Single Pattern Camshafts)
2009 = 14.00 (6-Speed Transmissions and Single Pattern Camshafts)
2010-2014 = 14.50 MPG (6-Speed Transmissions and Dual Pattern Camshafts with VVT)

The Average for all of the GMT900 SUVs is 14.37 MPG.

FuelEconomy.GOV lists the combined average for the 2007-2009 models as 16 MPG and for the 2010-2014 models as 17 MPG. Not!

 

[swathdiver]

So last night Justin sent over an updated tune. Not having done this before I pulled up the instructions and went out to the truck and installed them. I think. You see, I only turned the key to the accessory position and it ran through the paces and told me to turn the key off for 15 seconds. Did that. But later, I came back in and really read the instructions and I was supposed to have put the key to run and taken it out of the ignition when told. So I went back out and the AutoCal this time said to turn the key off, so I removed it, waited for the countdown and then did the TCM the same way too. When doing the TCM both times, all kinds of errors came up on the DIC, Traction Control, Trailer Brakes, etc. All went away when process completed.

After the first time, I took the truck out and averaged 18.2 @ 70 again five different points, from a low of 17.5 to a high of 18.9. I've read a lot about guys who put these engines in cars getting good mileage above 2000 rpms so later shifted it into M5 @ 70 for a long spell and she averaged 17.5.

So now I have to do it all over again. Was going to make a second run last night but the rains came and are still upon us.

Switching back to Mobil's gasoline, the alcohol content is down to 2% from 7-8% and that is sure to help mileage.

 

[swathdiver]

Next time out I'm thinking of pulling up on the Tech2 the engine load and torque to see why I get those differing numbers north and south on that part of the highway. I wish I had an inclination sensor, thought I'd seen one in the Tech2 before for the airbags but can't find it so the load % and torque should help give a better understanding.

Way back when AFM was new, guys with HP Tuners were tweaking it to run longer. They discovered that by manipulating the vacuum and TPS settings they could even accelerate slightly in V4 mode, even a guy with an Avalanche. I wonder if they're still around and driving these trucks 11 years later. Most of the posts are from 2007 and 2008, before everyone started turning it off. Some of these guys were getting mid 20s. One of the parameters for AFM to kick off is if the TPS hit 12%, well mine was cruising at 70 mph @ 30% so don't even know if it would kick on in stock form.

My TPS at idle is 8% again. When it cools down I'm going to finally put those breathers in and get that blowby out of my intake and TB.