An Interesting Result

[billxam]

I've always been a HP freak but also love to hypermile. My current vehicles are a Dodge Stealth R/T twin turbo and a 2009 Honda Civic. Recently, I've had a vibration in the rear of the Honda, my daily.  The dealership showed me the damage - steel cords showing and collapased shocks. Had them do the work and set out to see my MPG. Before, I was getting 34 mpg on the highway going from Ann Arbor to Gaylord, Michigan. Along with a horrible shaking, limiting speeds to 70 mph. Before the work, 70 mph was 2500 rpm. After, 2250. First trip to the above destinations netted 41 mpg @ 70 mph. The speed limit changes to 75 after Bay city so the overall fell to 38. Normally, the fill up at either end of the trip has been 7 gallons. This time, it was 5 gallons to fill.

[David64]

Shocks/struts and tires make a difference.

Something as simple as an alignment can make a difference, but many people don't think about any of that till something goes wrong and they have to spend thousands to fix it.
Oil changes, belts, hoses, spark plugs, transmission fluids, rear diff oil and if you have a 4 wheel drive, you need to change the front too....all that needs to be changed at regular intervals if you plan on a car lasting for very long.

That reminds me, the transmission fluid in my old Dodge is about due.

My new truck has Bilstein shocks.....I damn near had a seizure when I saw what new ones for that model cost. Yikes.

[Solvedit]

The reduced diameter of worn tires probably caused the increased RPM.  Alignment issues could cause tire scrub which cut MPG.  If the shocks were nitrogen-pressurized, maybe one end of the car or other sat a little low which caused greater frontal area.


Lately I have been trying to research if European engines which are spec'd for 5W-30 have the same ring, bearing and oil pump part numbers as US cars which are spec'd for 5W-20.  Some sites claim engines had to be redesigned to be able to run with the thinner oil.  They cited wear-resistant coatings on things like timing chains and larger rod bearings which in turn necessitated angled rod caps to allow installation.  If the oil-grade-specific parts were the same in the rest of the world, it would mean it was safe to use 5W-30.  Then again, some have claimed that 5W-20 is better all around and it is simply less available in other markets.

[rickymouse]

Reminds me of the old days, tagging semi's with my sixty nine mustang special edition with a 302 Cleveland and headers, duel exhaust, and a six fifty Holly double pumper on top of a high rise aluminum intake.  If I layed off the gas, I could get twenty five mpg but tagging a semi I got about forty mpg.

I quit that one day when a semi I was following turned on his flashers, then went sideways on the road and the driver came out with a tire iron.  I hit reversee, flew back, did a reverse spin and went back three miles to a restaurant in a little town.  I just looked up tagging, I guess they call it drafting these days, but then again, I am a Yooper, and maybe we are the only ones that called it tagging back in the seventies. 

I asked a friend who drove a semi how that guy knew I was tagging his truck, he said you can feel the drag when someone is doing it to the truck.  I could stop faster than a semi could  so I was not worried.

I used to love building up cars and was suprised how much better the gas mileage got when the thing was running so good...As long as the tires weren't spinning and you weren't racing or driving wildly.

Being so close to the back of a semi if you aren't really alert is not a good idea.

[argentus]

Where I live, there is nobody who can balance tires (tyres), so I have to do it myself by guess and by God.  It makes a huge difference.   I also regularly rotate the tires.  I don't often have use for a floor jack, but that is ultimately useful in such a situation and I think has paid for itself.

I buy the best quality tires that are available locally.   When I factor in shipping costs, it doesn't make a lick of sense to import better quality tires.

[MalevolentTwitch]

2009 Honda Civic having  3 options for transmissions (Automatic, 5 spd manual, and 6 spd manual)... We get the following...

Auto: 0.525 5th gear and a 4.440 Final
5 Spd: 0.727 5th gear and a 4.292 Final
6 Spd: 0.659 6th gear  4.76 Final 

Just use the following "shorthand" formula.... 

Tire Diameter = (Engine RPM x 336) / (Vehicle Speed x Total Gear Ratio)

...and you can easily see how much worn vs new tires can affect "low load cruising" engine speeds. If you want to know where the 336 comes from, I can provide the explanation.