i had a question about whether i need a tune up or not i have a 04 g35x and im just now going on 90,000 miles... this is my first winter with the car and im starting to realize that the car takes for ever to warm up in the mornings and that it feels a little sluggish when first starting up in the cold...i also been realizing my gas mileage has been horrible lately and i have been only driving 50mph or less and all highway and still...can someone tell me what can be the problem?

 

Cold weather decreases mileage in general.

A tune up will never hurt at 90k.

 

Get a block heater installed and your car will warm up just like as if it were summer.

But yeah if its cold out side usually takes about 5-10 to warm up. With a block heater its 3-4 minutes.

 

[QUOTE=kidgotheat;6237167]i had a question about whether i need a tune up or not \

clogged air cleaner, low air pressure in tires, need 35psi cold, check there first

 

By tune up what excactly do you recommend for it?

 

Old school tuneups are not applicable for the G. If you haven't replaced your sparkplugs do that first followed by changing all of your fluids and your belts if they haven't been changed in a while or ever. That's all you need to do. It's a good idea to clean the MAF sensor as well every 10K miles or so.

 

Does it reach full operating temperature? If not, maybe you have a thermostat that's stuck open. Check and replace the coolant temp sensor. If the motor is allowed to run cold it will continually run rich. Make sure your plugs aren't fouled. Make sure all the fluids have been changed by now. Make sure your air filter is clean. Check your primary O2 sensor. Maybe it couldn't hurt to change that as well. Try driving in a more economical manner as well.

 

Alright so I just changed all the belts about 3 months agoo .. So I will try replacing my spark plugs and changing all of my fluids... I will also try and clean my maf sensor...

Just wondering when doing my oil change should I use synthetic oil? Will that help a lot?

 

Couldn't have said it any better myself

 

Excellent post.

OP, you didn't post your real world mpgs so it's hard for us to get a handle on what may or may not be a problem.

The reason the car feels sluggish is because the ECU reduces power until the engine oil and transmission ATF reach a certain temp. It's to prolong these systems. Be happy Nissan did this.

Assuming the car is in good running condition, here are some things to consider:

1) G35Xs tend to get fairly poor mpgs because they're heavier, have deeper gearing, and have a bit more drivetrain rotational mass due to the AWD components. In the warmer months, expect about 16-17 in town and 22-23 on the highway. In the winter, it's not uncommon to see a 10 to 15% drop in MPGs. That means you're X could potentially see 13-14 city and 18-19 hwy.

2) Winter gas has results in lower mpgs because of variour additives to improve emissions. Winter gas alone can suck about 5% mpgs.

3) Cold weather kills mpgs because cold engines run very rich in attempt to warm themselves up quickly.

4) Cold weather makes ATF, oil, and gear oil very thick. This increases drivetrain drag until they're warmed up.

5) Short distance driving (less than 5 miles) will result in dismal mpgs, especially in cold weather for the reasons listed above.

6) DO NOT let your car warm up by idling. This poor practice will result in extended warmups, doesn't help warm up ATF or gear oils, does not adequately warm up the entire motor, can foul cats with excessive amounts of hydrocarbon, and will consume far more fuel. Ideally, the best cold engine warm up procedure in cold weather (30 degrees or below), is to start the engine and let it idle for about 20 to 30 seconds and let the oil get cycled a bit. Then drive sedately until the temp gauge is in the middle range. This will confirm the motor and tranny are at ideal operating temps. This warm up procedure is far quicker at warming up a motor and drivetrain and in the long run, much better on the car itself.

 

No.

 

This is usually what I do personally besides maybe the warmup time some days is a minute or two. What do you do when you make short trips during the cold weather, say in the single digit temps traveling < 3 miles. Let the car warm up just enough so when you get to your destination it is at operating temp? Or do you just do what's stated and shut the car off when you get there no matter what the temp of the car is?

I am just curious because I make a lot of short trips.

 

That's what I do. Let it run a little to circulate the oil and fluids, then drive slow. It'll be warmed up by the time you get there.

 

Wow thanks for this very imformative post .. I usually sit in the car until the temp guage reaches the middle than I drive off ... I will deff have to change that than and try what u said... And yaa during the summer I w as getting more mpg ... As for the actual real world mpg I'm goiing to see the excact numbers I get in a few..also does the gas I put in the tank matter so much I usually use premium but the person who owned the car before used to fill up with the most expensive gas he said does that change matter much?

 

Yep, definitely just let it idle for half a minute or so then get on your way. It's not going to hurt it if you start it and scrap ice, snow, etc as well. The idea is that you don't want to do idle warm ups.

The car will run on regular just fine, but mpgs could be reduced, especially in warmer spring/summer temps. In cold weather, it's probably not going to be as big a deal. Simply put, higher octane fuel is more resistant to burn and more resistant to pre-ignition (pre-detonation). When it's hot out, the engine is more likely to have pre-detonation because the engine and air temps are higher and it's harder for the radiator to shed heat. The way the motor combats pre-detonation is by adding more fuel to cool the combustion chamber. So, if you run 87 in the warmer months, the engine may be using more fuel to keep the engine cooler. Odd, I know. When the engine is cold and the air is cold, pre-iginition is less of a concern.