new to this forum. just bough an 08 G35. got it for a good deal. has 82,000 miles already though. i was wondering what the best cruising speed is to get the best mpg on the freeway?
also, with the amount of mileage, when would be a good time to get it tuned up? i used to use royal purple in my old lexus is300, so what should i use for my new G? I live in SA,TX, so its usually pretty hot for about 8 months out of the year. i need a lot of advice guys. Thanks.

 

Welcome to the forum.

Cruise at the posted speed limit. Faster burns more fuel. Slower pisses people off
Follow the OM for tune up/maintenance. It depends how it was driven by the previous owner, how you are driving it and the climate (Texas heat).
Nothing wrong with using RP engine oil. Lots of oil threads on hear for you to read.
The G is a pretty low maintenance performance sedan IMO.

 

I bought my 07 G35x at 82k miles and replaced the spark plugs with iridium. I was very surprised that I could tell a difference. Don't wait to 100k miles like the OM says IMHO.

 

Welcome to the site
My 09 w/ the 7speed auto gets nice mpg at 80 mph, almost 30mpg on the flat New Mexico, Texas, & Arizona highways if I'm not going against the wind. My 07 w/ the 5 speed got about 25-26 mpg going on the same roads at 80mph, but 70-75 mph w/ my 07 got about 1-2 mpg more. The 5AT spins about 500 rpm faster at cruising speed than my 7AT. I'd rather not discuss my city mpg

 

Thanks for the repsonses guys. So I'm thinking 70-75mph cruising speed should work for me then.

 

I agree with your point. They should be checked before 100k miles.
For the OP, This info is in not in the OM or the Service and Maintenance Guide. At least not in the 07 and 11 pdf books that I have.
The info can be found in the Infiniti Factory Service Manual (FSM), MAintenance section. It states a change interval of 105k miles.

 

I just hit 70k miles on my 06 coupe. I thought about changing the spark plugs but isn't it expensive/hard to do?

 

THe original plugs are Iridium plugs, so there was no enhancement there. Plug change interval is recommended at 105K miles, so you are a bit early on that. If your engine is running well, and kept in good tune, there no reason why your plugs should need to be changed at just 82K miles. Post a pick of your old plugs if you've still got them, I'd like to see them.



As for the OP's question, I have found that I get fantastic mileage at around 55 mph. The only trouble is I NEVER drive that fast unless I am totally constrained by surrounding traffic and must do so.

 

it seems like cruising at below 2200 rpm works for me to get decent mpg.

on a 6MT, that translate to just under 65mph

 

I did many tests on highway and I managed to get 27-29mpg cruising at 63mph (2600rpm). That is the best result cruising back and forth on the same highway. Gas mileage starts to decrease at higher speed.

 

All of your responses and input have been very helpful. For oil, I like royal purple, but what weight should I use?

 

^^ unless you've got some specific temerature related considerations, why not just use what the manufacturer recommended (5w-30).

 

I actually wonder this whenever I put gas in my car. I usually see my DTE going up whenever I'm in 4th, going about 40 MPH with the RPMs at about 2200-2500. Those are numbers when I'm in the city. I never really pay much attention when I'm on the highway. Maybe I'll take a look this weekend.

 

According to my Garmin Nuvi, 46 mph is the most efficient speed in my car. Not very practical however.

 

I had a Dodge Dakota and they used 0W20 from the factory to get better mileage, that stuff is water.