Driving faster than 70 mph: ride quality/MPG?

[98_Q45]

Just a random rant: but I live in a state where the speed limit is 70. I do 70-75 on highway Regularly. But I’m often getting passed by people doing 80/90. And it makes me feel I’m driving too slow lol. I have driven in 75 and 80 mph limit highways. I feel 75 is the sweet spot, 80 is nice when you’re on the open straightaway road during the daytime.

However, I don’t like feeling I have to stay over the speed limit all the time because: mpg starts to stop a lot above 70 mph. I have a GM v8 with mpg gauge: I’ve been able to squeeze out 27-28 mph going 65 mph versus 21/23 going 70/75. And even though it seems just a few miles, over a course of a tank of fuel: that’s probably $10 savings, not to mention I drive a lot of miles every week so the savings is even bigger.

I also notice handling and overall vibrations above 75 mph gets a bit sketchy lol. Idk if it’s just because it’s older car and doesn’t have stability control option. But I drove a friend’s 2019 Cadillac, and even though it felt smooth even at 100 mph (briefly, not the whole route), the steering and overall stability was better at 70-72 mph.

I wonder how are people flying by so fast all the time lol. Not to mention there’s always so much crap in the roads especially during the summer and weekends: I’ve had to dodge numerous tires, animals, stuff that fell off pickups: I do not like driving faster than 75 anymore. However, the Q seems to fly past cars fairly well in the city where the limit is 55-65. I just don’t like flooring it on every acceleration or going 85, because it will use so much gas.

[VStar650CL]

The vast majority of state troopers in the vast majority of states give you +14 mph, so for most purposes that's the "real" speed limit on US interstates. Local and county cops can be different, and in some places the stroopers let those guys chicken pick on the freeway, so I always keep it to +9 when I'm in an unknown jurisdiction. What's funny (and the insurance companies know it) is that the safest category of drivers statistically are those driving +7~14, so by rights a local ticket for +10 should decrease your rates. Free money for Progressive and Allstate.

Speed doesn't kill, speed differential does. Keep up with traffic, folks.

[fontana dan]

The Q likes to go really fast. It is a sleek, low, and steady machine. I think anywhere between 75-90mph is a happy place for the car to cruise, road safety and speed limits aside. Should be smooth as long as everything is balanced and tight. MPG suffers a bit. Lean into the gas more and the car will do 115 without downshifting or unlocking the TC.
I had mine up to 130mph once, WOT, it had just shifted into 4th gear and kept pulling but I ran out of road.
At night I get a little nervous driving faster than 70mph because I'm out-pacing my headlights. Brights are good but low-beams leave some to be desired even after replacing bulbs and polishing the lenses.

[98_Q45]

I agree, speed differences seem to be the most accident prone conditions. I don’t mind driving the speed limit, but I can’t stand when someone is driving 55 mph at night, with dim taillights on a 75 mph highway.

I did once get stopped doing 76 in a 55: and went to jail (different vehicle lol). But that was so bogus, and ever since I just been a bit leery. I’ve had a couple other speeding tickets that were dropped, but overall it’s just a lot of hassle and even 10 mph over the limit is risking it. I have found, as long as I’m within whatever the first digit of the limit is: I’m okay: but there’s still a bit difference between 59 in a 55 versus 79 in a 70.

Regarding headlights: I just polished and re-aimed mine the other week. They get clear but I have to do it every month at least or they start to fog up again, but it’s all outer surface residue (and I’m just using basic plastX, not all the fancy buffer kit stuff). However, I was able to buy brand new headlights for my Maxima that are sparkling clear. It sucks they don’t make aftermarket ones for the Q.

I’ve pushed the Q to 114 mph a few times myself lol. Seems there is a limiter. However: I feel like everytime I push the Q to the Max: something breaks lol. Just last month, a heater hose coming out of the engine sprung a leak, and the car almost overheated AGAIN. I had to drive like that for a week until I was able to get home and figure it out: and of course it’s a discontinued part. The next day I came outside, rear tire was completely flat. I don’t have the most expensive tires, but I notice I’m always getting nails and flats on the rear wheels more than any FWD car I’ve had.

I just prefer driving my car normal, and occasionally flooring it: sucks because when I put 91/93 I should be flying past everybody but, I can’t do that all the time.

[Benjy67]

Since you're talking about driving faster than 70, I am soon to be the pround owner of a 1996 Nissan Cima which is mechanically identical to the 1997-01 Q45. However as you are probably aware, JDM cars have their cruise control limited to 62 mph max.

Is it possible to flash the ECU or get a new ECU to circumvent this limitation?

Any leads would be deeply appreciated.

Thanks

[Q451990]

to NICO Benjy67!

I wasn't aware of the cruise control limit. Hopefully someone will chime in with an idea of how to get around that.