[Efthreeoh]

So the point of all this writing is to convince you that dailying the Z4 is not going to be painful maintenance wise.

I'd like to add my 2 cents since I have some relative experience here. I drive a lot; 35,000 per year just for my work commute. I have a 2008 3.0si Coupe (bought Dec. 2014), a 2005 E46 330Cic (recently bought Sept 2019), and a 2006 E90 325i (bought new in May 2006). My daily commute is 170 miles a day(round trip) which is a mix of awesome back country roads, dual lane rural highway and stop and go dense highway traffic. I DIY all maintenance and repairs on all my vehicles. All my cars are manual transmission versions.

Beginning in October 2007 I ran the E90 exclusively for the daily commute, and it now has 397,360 miles on it. If you don't know, the E90 shares the same basic N52 (engine) that is in your '06 Coupe. The '06 E90 325i does not have the Z4 3.0si DISA-valve 3-stage intake manifold, other than a slightly more open exhaust manifold the engines are mechanically identical. The N52 in my E90 saw BMW's extended oil change intervals; between zero and 221,000 miles the average OCI was 16,300 miles, now at 397K, and a decision to shorten the OCI to 10,000 then (recently) 7,500 miles, it is still above 12,000 miles average. The E90 has seen only BMW brand 5W-30 oil and original equipment oil filters (MANN HU816X).

In December 2014 when the E90 was reaching 270,000 miles I picked up the 2008 Z4 3.0si. I bought it as a backup to the E90 because I was anticipating the E90 was going to need some surgery and needing more repairs that would keep it off the road for long durations (I was wrong - LOL). The Z4 had just 23,000 on the clock when I bought it. Sharing the daily commute with the E90, almost 6 years later the Z4 has reached 107,200 miles. In that time the Z4 has required normal maintenance. I've changed the engine oil every 10,000 miles, biennial brake fluid flushes. I've changed the diff and trans fluids at 38,000 and again at 100,000 miles. New spark plugs at 100,000 miles per BMW schedule. I replaced the serpentine belt and tensioner at 105,000. I flushed the coolant at 77,000 miles. The brakes, front and back, came up due at 95,000 miles. And I've replaced the engine airfilter twice. The N52 is known to leak oil at the valve cover, oil filter housing, and the oil pan. At 107K the N52 in my Z4 is dry at the oil pan and valve cover, and a very slight leak at the oil filter housing.

Finally, just to tie in with your experience in owning a E46 with the M54 engine, since September 2019 when I acquired the E46 at 100,000 on the odometer, I've driven the E46 20,000 miles. The M54 is a little weak in the cooling system and intake/vacuum boot/lines. My car had some of those common issues taken car of by the pervious owner, who I know quite well, so at 100,000 miles I baselined all the fluids: trans, diff, and brake fluid. Since then, just oil changes for the E46.

My experience with the N52 is the engine is pretty much built for tank duty. Yesterday I just did oil change No. 32 on the E90 and took it out for a 10-mile leak check. The engine at 397K pulls as good as it did the day I picked up the car in May 2006 and has not dropped off in fuel consumption. Truly an amazing in-line six from BMW. The chassis of the E86 Z4 is probably one of the best offered by BMW. The Coupe chassis is extremely stiff, so it doesn't flex, which means it will not weaken over time and high miles. My Z4 chassis has remained virtually unchanged in the 6 years and 85,000 miles I've owned it. I have the Msport seats with extended leather and the interior has barely shown any wear from daily use.

So other than your car having very low miles, which if you keep them low the value of it will only increase over time. I went through that same issue when I bought my Z4. Once I bought it I realized what a fantastic car it is. I didn't want to rack up miles on it, but in the end, I bought it to drive it and preserve my E90 as long as possible. So here it is 6 years later at 107,300 miles and seemingly barely more used other than numbers increase on the odometer. Maintenance and wear wise, I doubt there is a better BMW to daily than an E86 Z4 N52 Coupe.

Apologies for the long post.