Highway, is it really flat long stretches or are you climbing up and down hills. This makes a pretty big difference.

On older cars, MAF cleaning, throttle body cleaning, plugs, engine temp sensor, of course the filter. Run a bottle of MMO through a few tanks of 93 or 91. Bad O2 would give you a code. Some replace as preventive maintance. At 70 mph on a fairly flat surface if you can't average at least 24 mpg something is wrong.

 

Your demur is based on what personal experience with NGK's next generation Ruthenium spark plugs that you care to share?

Here:

https://patents.google.com/patent/US20120169206

 

Are you serious, or joking? I cannot tell. Sometimes humor doesn't come through effectively on a forum. If you're being serious, maybe bitog, but that's all.

 

Where is your information on Ruthenium plugs?

 

I wonder how much longer we will hold out. For me, I get 19.x all day long for 3 years of commuting--reliable and valid.

Modern cars (too many to name, Altima, Accord, Camry, Sonata, CX-5, Santa Fe, on and on), which I rent 2-4X per month, are now doing around 26-27 with the same type of driving. We get excited to do 28 on the highway, to which the modern cars do 38-40. How much longer are we willing to burn premium with our LS' (rhetorical)?

 

Great idea! This test was more difficult than I expected. Found out that the instantaneous mpg is VERY sensitive to ANY elevation, even a slight bump on the road. I tried this late at night on the freeway (in Houston, which is relatively flat) at 45MPH and 65MPH with cruise control on and occasionally switched over to S mode to make sure it was in 6th gear. The instantaneous varied from 15-40mpg. On the straightest stretches, I want to say it was 27mpg-ish but I can't say that for certain. I don't think I've ever reached 30mpg, even on long road trips. I agree with everyone here and bet its the city driving thats dragging my mileage down a lot.

 

Also, since my car is at 170K miles with practically nothing replaced, this is what I plan on doing this month in this particular order.

1. Seafoam
2. MAYBE Engine Restore (but probably not since I'm scared it will mess things up)
3. Replace all factory plugs with NGK Ruthenium (not b/c I believe the marketing hype but rather b/c they are $1 more than iridium plugs and I'm genuinely curious)
4. Replace all struts & springs (they've been gone for a long while but the ride's not awful)
5. MAYBE replace coolant temperature sensor since it seemed to work for other people on the forum
6. MAYBE replace a fuel pulsation damper. 1 bank is at 2%, the other is at 7% which i don't think is awful but I read should be lower.

I have a strong feeling nothing will increase my MPG but i'll do them one at a time and let y'all know if I'm blessed with a miracle lol

 

That's good to hear, and indicates your car is totally normal.

 

Try buying a new OEM MAF sensor. Also put in some fuel system cleaner like Redline. My car was really sluggish recently and I cleaned my MAF like crazy the proper way, used redline and reset ECU. In just about a 1/4 of a tank so far there is a big difference back to how my car used to respond. I need to check my MPG since I did that.

 

Clean the Vacuum Switching Valve (VSV) too, there is a DIY thread on that with recent posts.
Make sure your tires are properly inflated. Rolling resistance can vary widely between different tires. I switched to a Pirelli All Season tire a year ago and immediately lost 1-2 mpg from the previous worn out Hankook tires (sp?) that were on there. The traction and wet braking gain and quietness of the tire made the switch worthwhile.

I cleaned the MAF sensor as suggested above (quick and very easy) I think I got an immediate mpg boost but was doing so many upgrades/tune-ups at the same time I can't quantify it. The throttle response seemed to be improved. Ran some Chevron Techron fuel system clearer through the tank too . . .

I also have the option to buy 87 octane pure unleaded gas (no ethanol) from the local Cenex station and my all-time best mileage came from a tank with mostly that in it. Since then I switch between Cenex Regular and Mobile premium (92 octane).. Ethanol has a lot less BTUs in it than pure gas so with 10% ethanol you are already taking a hit of a few mpgs..

I think if I really wanted to hypermile my '05 I would drive it like it had a 60 hp four banger in it, and drive like a poke but that's not going to happen, I have a better vehicle for that.. .If you frequently take advantage of all or most of the power available from the 3UZ be prepared to pay for it at the pump. The instantaneous mpg readout will tell you all about it.

 

btw octane and mpg have no relationship, that's not what octane measures.

I spent a week in a brand new Altima. It was surprising to me how easily the car did 40 mpg highway (when we get all excited about 28). Now I got a brand new Maxima and to the Altima's 40 it gets about 31. That's a steep penalty! Suddenly our 28 isn't so bad!!

But look at this screen on the Maxima I have now. This tells you a little about how it achieved its mpg. Such as over how far, and avg mph. Funny how the car had 148 miles on it when I took the pic, as it only had 4 when I picked it up. Been getting brand spanking new rentals lately which I have to admit I like.

 

HOLY SMOKES!! Tire pressure, perfect. Cleaning VSV did nothing. Cleaned my MAF sensor and mpg shot up to 27.5 (previously 21) over a 40-mile trip (and still climbing). I didn't want to waste anymore gas so I stopped but felt like it could have reached 30 mpg if I had kept going. What I discovered is that my car really likes going around 65-70mph, 6th gear, 1900-2000rpm. I'll have to play around some more to find its peak but definitely very happy right now! THANK YOU everyone for your valuable input

 

Just drove 2,000 miles in the last 10 days during roundtrip South to the Midwest. Running a mix of mid-grade 89 and premium gas we got around 25.4-26.7 between fill ups running approx 75mph.

My long term fuel average (mix of in town and highway with no heavy traffic) from the computer, and which I almost never reset, has for years averaged very steady at 21.1 - 21.3.

I am happy with overall mileage on the LS since I drive less than 10k per year at most. BTW because of transaction costs - buying a new car to save money on gas makes zero financial sense unless you drive at least 20k miles or more a year.

I drive my car in a manner that is careful about gas mileage - smooth starts, always looking ahead to minimize braking, no tailgating, no aggressive or typical asshat style driving behaviors, etc.

 

Thank you for the tip to potentially swithch to Ruthenium for additional benefits for 3uz-fe and possibly transmission.

I would like to go ahead to and test these claims by the end of the next week. I ll share the information here whether I see an improvement or not.

 

I remember that back in 1998, there was a sticky on how to increase HP on the Maxima. The easiest way was to drop in a K&N Panel filter which at the time cost about $55 (Lol). Then there was a cleaning kit for about another $10. The sticky/grid said you get 2-5 HP out of it. I was one of the many idiots who believed it. I was so irritated that my mpgs dropped I actually bought a 2nd K&N to see if the results would be any different. We all get fooled at least once in our lives (many times just usually not 2X on the same issue). I was glad when that guy with the 3 mil. bench test equipment proved K&N was snake oil. Most people don't have a 3 mil. piece of equipment so snake oil is able to generate sales. How about Techron on DI engines?