Fuel Mileage Differences- 1998 vs 2004 Frontier

Both trucks have the same engine, right? And they have same tranny? If so, my guess would be O2 and perhaps the ignition timing is off on the

2004 as well. Check the timing first.

CD

How about details on the two trucks - engine transmissions, etc.

According to the information at

the best 1998 Nissan Frontier (2WD, 2.4L, 5 speed manual) was rated 20 city, 24 highway by the EPA (new rating system). User estimates averaged 22.5 mpg (based on 5 estimates from individuals). The highest user reported mileage for a 2004 was 26 mpg, the lowest was 20 mpg. A 2004 with the same engine and transmission was rated exactly the same by the EPA, and the user estimate was slightly higher (26.5 mpg). The worst 2004 Frontier, V-6, 4WD (either transmissions) was rated 13 city, 17 highway by the EPA (user estimates were 15 mpg). The 2004 V-6 2WD Frontier was rated only slightly better (14 city, 17 highway).

So, if both of your Frontiers were 4 cylinders, more investigation is warranted.

Do both vehicles have the same size tires? Are the tires the same size/type as originally installed on the vehicle (you don't have LT tires instead of P tires on the 2004 for instance)? Do you know the rear axle ratios? Have you checked the odometers to be sure they are reading correctly (or at least the same)? Do you check the fuel economy over multiple tanks of gas?

I have a 2006 V-6 4WD Frontier. I am averaging around 19 mpg with a lot of highway driving (but at relatively high speed). The mileage you are claiming for your 1998 seems high compared to the EPA estimates. On the other hand, your reported mileage for the 2004 (assuming it is a 4 cylinder) seems low. If I was going to "guess" at a problem, I'd recommend the following:

1) Check the odometer (either against a measured mile, or a know distance measured by your 1998 truck).

2) Make sure you don't have a brake (or brakes) dragging.

3) Have someone check the exhaust back pressure. I don't know if there is a port for that on your truck, if not, experts know how to drill a hole to check back pressure. A plugged catalytic converter could affect both fuel economy and performance.

I doubt your problem is the oxygen sensor, but you can have it checked.

Ed

Thanks for the input. My 1998 does seem to have narrower tires- I'd have to compare details yes, multiple tanks of gas. If anything-I now know for a fact that I was getting ripped off on gas, seems like on a 12.75 gallon tank, with 1/8th left- the station said it was delivering about 13-13.25 gallons of gas, so that changes the numbers about 10% to get us back down to the realistic rates on the 98 Frontier.

One thing is for sure- I drive both cars the same mileage (equidistant between the train station and home or train station and work. The 98 beater is at work- I go out to lunch and may put 5-10 more miles per week on this vehicle than the 2004, and I seem to be filling up the 2004 tank 1/3rd quicker (fillup every 2 weeks, while the 98 only needs gas every 3-3.5 weeks.

I ran teflon oil (slick 50 for about 3 oil changes in the 1998 around

50-75,000 miles)

The 04 stats seem disappointing- not sure why Nissan would step backwards. Both engines are automatic, 4 cyl...will have to check sizes and weight specs I would suspect the tendency to ping and being sluggish seem to be at the root cause. I asked the dealer about computer settings,etc.... since I bought the car used with >30,000 mi, My fear is that the truck has some problem the dealer does not want to cover under warrantee, and will discover it as soon as the truck is outside warrantee. Thanks for the inputs. I will be sure to check them out. Thanks

messagenews:46af32a1$1@kcnews01...

YoYeah, the dealer's avoiding something. Bear in mind that even though these are the same vehicale with tranny and engine, the 2004 may be heavier in a few significant ways.

1. The standard rims. It looks like your 98 had 15" rims and the 2004 has 16" Bigger rims hurt gas mileage. Rotational mass goes up significantly. Also, your 2004 may have bgiger brakes, side curtain airbags etc. The rotational mass and total curb weight of the 2004 will work against it in terms of gas mileage.

Take my car, a 98 Sentra 1.6. The 1999 model came with 14" rims. The

98 model had 13" rims. EPA mileage for the 99 went down 1 mpg compared to the 98 because of that.

CD