About to give up on it... - Altima Forums.net - The Nissan Altima Enthusiast Talk and Discussion Forums

AltimaSL · 09-03-2008

Yet another problem has occurred. My MPG avg. display is off by 7mpg. I thought no big deal, take it to the dealer have them do their thing, take it back. NO. I was there for over 2 hours. I brought it to the dealer and he, the service rep, said it was because i had low tire pressure. HUH? That doesn't even make sense. Maybe he should do more WORK and less EATING. He was a lazy, fat, idiot who obviously didn't care about anything but himself. So i got the manager out, told him about the fat guy, then asked him to look at my car; he said he would fix it. So he "fixed it". I wonder if by fixing it he meant HOLDING IT FOR THIRTY MINUTES AND GIVING IT BACK TO ME. He didn't TOUCH my car. I will be calling Nissan and reporting this dealer. I am seriously considering giving up on the car and trading it in for an Accord. This is sickening. My car is only FIVE MONTHS OLD. I know warranty covers this, but it is the constant trips back to the dealer. I have to go back for their mistakes. Thank god i got such a good deal on my car. over 1k below invoice. I won't lose "that much" with the trade. I haven't yet decided, but i am VERY tempted to do the trade.

PhuckinPhil · 09-05-2008

how do you know it is 7 off?

VictorE1123 · 09-05-2008

I have the same type of issues with the Nissan dealership in my area. I made an an appointment in person to have a hybrid emblem replaced, I go to drop off my car and wait for the shuttle ride home because the rep said would take a few hours. After about 2.5 hours in their waiting room, she comes out telling me they don't have the part in stock and it'll have to be ordered. Never an apology for wasting my time. Complete incompetence...

luxuryrules · 09-05-2008

Yes, low tire pressure can cause this. The computer uses a function of the VSS and fuel consumption via fuel injector timing to figure out your fuel consumption per mile. The important part is, since it uses a VSS on the transmission, the only way the computer can be accurate is if the tires are the stock diameter. The computer knows that, for every rotation of the VSS, based on what gear ratio it is running at and the diameter of the tires, how far the car has traveled.

Obviously, if the tires are low in pressure, then they are not the intended diameter and, for every rotation of the tire the computer thinks the car has traveled farther than it really has. Thus, the optimism of your trip computer (and it also means your speedo is off). I put smaller tires on one of my cars back in high school, and not only was my speedo off but that also threw off the mpg calculator. No big deal.

But, in all fairness, 7mpg is quite a way off for tire pressure to be the only culprit. Then again, of all the cars I have owned with mpg calculators, not one of them has ever been correct, ever. Heck, on the Altima in my sig, the calculator is off by 3-4mpg.

You can troubleshoot my theory by simply speeding and seeing what the cops' radar gun says.... (not recommended). Or get another car with a known accurate speedometer and have them pace you on the highway to see if your speedos match. If not, then the guy was right (or your VSS is broken). If they're spot on, then I am incorrect and it's back to the drawing board.
But I honestly don't know what else would really throw off the speedo sensor that much, do you have any ideas?

rtking · 09-07-2008

Quote:

Originally Posted by luxuryrules

You can troubleshoot my theory by simply speeding and seeing what the cops' radar gun says.... (not recommended). Or get another car with a known accurate speedometer and have them pace you on the highway to see if your speedos match. If not, then the guy was right (or your VSS is broken). If they're spot on, then I am incorrect and it's back to the drawing board.

Actually, just get a stand alone GPS unit (such as a Garmin Nuvi or Magellan Roadmate) and validate your speedometer and odometer against the GPS. It's normal to have a little variance (e.g. reading 60 mph when your GPS clocked speed is 58 mph, etc.)

As for the car itself, I can't stress how important it is to find a good service facility. My brother will NEVER buy another Nissan (and cautioned me from buying one) due to the numerous incompetent dealer service departments he'd been to. Having come from a long line of Ford vehicle ownership (and equal share of incompetent dealerships), I was kind-of used to it. But it was a breath of fresh air to find an excellent service manager who really took care of things.

I recommend hunting around until you find a service advisor/manager that you can work with. That makes all the difference. The car itself is pretty sound. It's really the crappy dealer service department that sours the experience IMO.

BTW, the excellent Service Manager/Advisor I like is Peter Gohil at Stadium Nissan. He was formerly at Douglas Nissan in Huntington Beach (which is now Surf City Nissan.) I've had good experiences with Angie at Surf City Nissan as well.

AltimaSL · 09-07-2008

Quote:

Originally Posted by PhuckinPhil

how do you know it is 7 off?

I calculated the mileage I got. It was 7 more mpg than what i calculated.

AltimaSL · 09-07-2008

Quote:

Originally Posted by luxuryrules

Yes, low tire pressure can cause this. The computer uses a function of the VSS and fuel consumption via fuel injector timing to figure out your fuel consumption per mile. The important part is, since it uses a VSS on the transmission, the only way the computer can be accurate is if the tires are the stock diameter. The computer knows that, for every rotation of the VSS, based on what gear ratio it is running at and the diameter of the tires, how far the car has traveled.

Obviously, if the tires are low in pressure, then they are not the intended diameter and, for every rotation of the tire the computer thinks the car has traveled farther than it really has. Thus, the optimism of your trip computer (and it also means your speedo is off). I put smaller tires on one of my cars back in high school, and not only was my speedo off but that also threw off the mpg calculator. No big deal.

But, in all fairness, 7mpg is quite a way off for tire pressure to be the only culprit. Then again, of all the cars I have owned with mpg calculators, not one of them has ever been correct, ever. Heck, on the Altima in my sig, the calculator is off by 3-4mpg.

You can troubleshoot my theory by simply speeding and seeing what the cops' radar gun says.... (not recommended). Or get another car with a known accurate speedometer and have them pace you on the highway to see if your speedos match. If not, then the guy was right (or your VSS is broken). If they're spot on, then I am incorrect and it's back to the drawing board.
But I honestly don't know what else would really throw off the speedo sensor that much, do you have any ideas?

I see where you are coming from and all, but how can that possibly make it 7 mpg off? I would expect maybe 2-4. My tires were only 4 psi under recommended psi on the front tires, and rear left tire. The rear right tire was 2 psi under the recommended level. That really doesn't make sense imo.

luxuryrules · 09-08-2008

I agree, 7 is a lot, but it is likely a combination of the tire pressure and the fact that those things are never accurate.

From here: keep a spreadsheet with the date, odomoter, volume of fuel, and cost per gallon every time you fill up. With it, you can calculate all kinds of cool car-geek stuff like mpg by tankful, lifetime mpg, cost per mile, etc. The important figure is the mpg by tankful - now that you have corrected your tire pressure, go five or ten tanks. If it is consistently 7mpg off, then go to a different dealer and make them look at it. I'm more inclined to believe it will be 4-5mpg off now that the tire pressure is corrected, but solid data is the only way we'll know for sure.

But remember that those things are usually not even close to accurate. I think if you can consistently get it within 3-4mpg of your actual mileage, you will be doing pretty good.

Just to double check, your car is bone stock, yes?

AltimaSL · 09-08-2008

Quote:

Originally Posted by luxuryrules

I agree, 7 is a lot, but it is likely a combination of the tire pressure and the fact that those things are never accurate.

From here: keep a spreadsheet with the date, odomoter, volume of fuel, and cost per gallon every time you fill up. With it, you can calculate all kinds of cool car-geek stuff like mpg by tankful, lifetime mpg, cost per mile, etc. The important figure is the mpg by tankful - now that you have corrected your tire pressure, go five or ten tanks. If it is consistently 7mpg off, then go to a different dealer and make them look at it. I'm more inclined to believe it will be 4-5mpg off now that the tire pressure is corrected, but solid data is the only way we'll know for sure.

But remember that those things are usually not even close to accurate. I think if you can consistently get it within 3-4mpg of your actual mileage, you will be doing pretty good.

Just to double check, your car is bone stock, yes?

Yes, it's completely stock.

luxuryrules · 09-11-2008

We got any follow up? I'm guessing you've burned a few more tanks of gas by now. Have you been tracking your economy by hand? Has it improved with the tire pressure change? Is the calculator still way off? And, if so, are there any other Nissan places out your way that you can get to take a look at it?

I'm curious to see what this turns out to be. I don't think it will ever be that accurate, but don't see what could really be broken.

AltimaSL · 09-11-2008

Quote:

Originally Posted by luxuryrules

We got any follow up? I'm guessing you've burned a few more tanks of gas by now. Have you been tracking your economy by hand? Has it improved with the tire pressure change? Is the calculator still way off? And, if so, are there any other Nissan places out your way that you can get to take a look at it?

I'm curious to see what this turns out to be. I don't think it will ever be that accurate, but don't see what could really be broken.

I have no idea of whether it got more accurate or not. The whole screen doesn't work now.

THE ICING ON THE CAKE.

PhuckinPhil · 09-11-2008

Quote:

Originally Posted by AltimaSL

I have no idea of whether it got more accurate or not. The whole screen doesn't work now.

THE ICING ON THE CAKE.

Doesn't sound good, I hope it's an isolated incident.

AltimaSL · 09-12-2008

Quote:

Originally Posted by PhuckinPhil

Doesn't sound good, I hope it's an isolated incident.

Well i went to another dealer. They reset it and got the screen working and reset the mpg calculator(idk if it works as of yet). They were MUCH nicer.

rtking · 09-17-2008

I wondered why my gas mileage was erratic on my Altima Hybrid. Except for 2 fill-ups, I used the same gas station every time. This time, I had "20 miles to empty"... which I knew from experience translates into having more than 2 gallons left in the tank. But when I filled-up the car, the pump stopped at 19.951 gallons. NO WAY. The Altima only holds 20 gallons and the most I could possibly pump would have been 17.951 gallons if I followed my "2-gallon remaining "assumption.

If I used the gas station gallons to calculate mileage, I got less than 30 mpg (29.xx mpg). My on-board mileage computer said 33.4 mpg. If I used "my guestimate" of a true 17.951 gallons, I got 32.56 mpg. That gets me MUCH closer to the car's computer. I'm beginning to doubt the mileage computer less.

I am not filling up at that gas station anymore.

Budperm · 09-18-2008

I hope that the new dealer took care of you RIGHT! As for RTKING's observation concerning pumped gallons vs expected or estimated capacity I ALWAYS pay attention to what the pump says vs what I think I need to top off. All pumps have an accuracy tolerance. I usually try to use the same station to fill-up and I will try every pump there. It shouldn't take but a couple of fill ups to determine which pump is the most generous. I use my trip meter to track miles per tankfull and weight that against the computers MPG per tank. The only time I pumped 19.5 gallons I was at 550 miles and showing 29.6mpg. If you do the math it all agrees within reason. I have seen some big differences in pumped gallons between pumps at the same station so paying attention will save you $$.

Knowing the station is critical too. I have seen the following done to maximize profits: added waste oil, water, deisel (when it was cheaper than 87) to storage tank. I have NEVER seen a station manager so mad as when a new delivery tanker driver put 5000 gallons of 93 in the 87 tank! Granted that all this happened in the older full service stations and is less likely to happen in gas & go stations but you never know!