1st oil change no MPG increase?!?

[KandyRedCoi]

OK this might have been covered before so forgive me.

i recently did my 1st oil change on my 2008 #6 touring @ 4500miles

before the oil change i was getting around 42-43mpg 90% hwy @ 75+mph
i dont drive the FE way, and i left the tires psi to the oem settings

after a full synthetic mobil1 oil change, the car still gets 42-43mpg in the same driving situations as i mentioned above

from what ive read before, people typically see an increase in mpg after their oil change

should i be worried? did i do something wrong? any suggestions and comments are welcome

thanx

[Sheepdog]

speaking purely for myself only I can suggest that you:

1. boost air pressure in the tires. 42/40 is where I am going.

2. slow the heck down! 75+ is illegal almost everywhere! Try 55 or 60. You would be amazed at the mpg difference.

[KandyRedCoi]

lol thanx 75mph is usually the flow of traffic where i drive, and yes i know its bad, ill try my best to slow her down

next step is to increase tire psi...not much since i dont want to affect the car handling and grip too much

anything about the oil change itself tho? from anyone else?

thanx

[richard schumacher]

Nope, that's about it for oil. Higher tire pressure should help noticeably.

[dwdean]

All I can add to this is that in the very limited experience I have driving at those speeds, FE in the low 40s is about right, synthetic oil or not.

This is about aerodynamics not the mechanical workings of the engine. I wish I could remember the thread on here where I read this so I could give credit where it's due, but I can't, so kudos to whoever said this first.

Imagine the following:

• You have a bucket of water.
• If you take your hand, spread it as wide as you can and then very slowly press your palm down into the water, the water moves out of the way and you hand goes into the water with no problems.
• Now, imagine taking your hand, again spread wide, raising it over your head and slamming it down onto the surface of the water. You can probably predict what's going to happen: one, water everywhere, two your hand is going to feel like you just slapped a brick wall.

Those two results are representative of any object moving through a fluid environment. Yes, for this purpose, the gas in the atmosphere around you can and should be considered a fluid, just like the water in the bucket in the analogy.

At lower speeds, even objects with relatively high drag coefficients (i.e. your spread-wide hand) will pass with little resistance. However, at higher speeds (i.e. you trying to spank the water), the fluid properties change and it does become rather like hitting a brick wall; you’re literally trying to force the fluid out the way rather than letting it flow around the object.

The place where that transition (from flow to force out of the way) occurs is a property of the fluid, not of what you're trying to move through it (yes shape does have some mitigating influence, but it's not huge). It turns out, that for air the first such transition is around 55 mph.

I know, everyone hates that number. The "man" didn't make it up to get us to all conform. It really comes from the simple fluid dynamic principles. Yes, there are other transition speeds for air, but unless you're talking about delta-winged aircraft, they're not important.

You might get small gains by changing mechanical things about the car (your oil, etc), but until you accept the reality of physics, you're not going to see big gains. Like most things in life, FE isn't free, you can have it, but to get it you have to give up some driving habits that probably aren't very good anyways.

Ask yourself this, if you drive 20 miles one way to work every day, how much longer does it take you to travel that distance at 60 mph as opposed to say 75 mph?

Do the math. The answer will surprise you. (To get time in hours, divide your distance in miles by the speed in miles per hour. To convert time in hours to time in minutes multiply the fractional number of hours by 60.)

[a priori]

Originally Posted by KandyRedCoi

. . . anything about the oil change itself tho?

Many folks (myself included) experienced a drop in mileage after the first oil change. The reasons? Could have been too much oil or it could have to do with the tire rotation. Sometimes the tires are a bit "sticky" at the beginning, so mileage often will increase with greater tire wear.

Maybe you've just conquered the MPG drop by improving your driving techniques!?

[KandyRedCoi]

LOL thanx for the input everyone, i will try to increase the tire PSI to my own specs and report soon after i get good test results

thanx

[edthefox5]

I moved to Mobil 1 at 1000 miles and have never seen an increase in mpg with an oil change. Have tried 10-30 and then moved to 5-30 with no difference in mpg's. Now tire pressure is 5 mpg's one way or the other.

[9G-man]

There is no magic formula you can pour into the engine and get better MPG.
If your goal is truely to increase your gas mileage, then you must slow down. Get out of the left lanes and discover a new, slower paced and better life in the right lanes.
Pump up your tire pressure.
Learn to manipulate your Prius at will, with Glide, stealth and warp stealth techniques.

Have fun

[N3FOL]

Originally Posted by KandyRedCoi

lol thanx 75mph is usually the flow of traffic where i drive, and yes i know its bad, ill try my best to slow her down

next step is to increase tire psi...not much since i dont want to affect the car handling and grip too much

anything about the oil change itself tho? from anyone else?

thanx

You are in SoCal so I would assume that you should at least be getting 50 mpg and up. The fastest I go on my Prius is 70 mph and my average is staying above 50 mpg. So, slow down a bit. You'll see the difference.