Dave, as I mentioned, there was (at least at one point) an actual taxi version of the CV, which was very similar to the CVPI. It even had the taxi yellow as a colour option. There were a couple minor differences between it and the CVPI, but they were negligible. The taxi version did offer the bench seat, whereas the CVPIs had front buckets. CVPIs offered rear seats in vinyl or hard plastic; the taxi version had the vinyl, and probably a cloth option. There wasn't a lot of difference in the drivetrain. Perhaps gearing might have been different; perhaps a different limited slip option may have existed. The CVPI may have had stouter brakes, but the cooling and electrical systems were the same, since taxis have similar cooling (i.e. lots of idling) and electrical requirements (radios, signs, lighting, accessories).
And when a police car does go WOT to catch a speeder, it's not the very instant after the car was turned on for the first time in the day, either. The oil will very likely be at temperature.
A lot of fleet vehicles, be they police, taxi, or something else, rarely have their oil levels checked, and that's where the danger lies, if you ask me. That's where I've seen the vehicles peter out. I'd rather go 6,000 miles on a full sump that's checked every day than go blindly on a 3,000 mile OCI, where the only time the dipstick is pulled is at the oil change itself.
If I were suddenly put in charge of a police fleet and there was some concern about funding (i.e. trying to balance oil change costs versus blown engine costs), I'd say I'd have to go the UOA route. Taxis and police are similar, yes, but there are subtle differences, as we've both pointed out. Running cabs, I was able to do all the oil changes myself and personally check the dipstick daily. In a police fleet, it might be harder to monitor oil levels, so some kind of documentation might be needed. Oils are better; fuel dilution with gas exists, but did not with LPG. So, to know whether the fuel dilution trumps the better oil, only a UOA could say.
Truth be told, it would be hard to fault someone for following the 3,000 mile severe service interval (assuming that's what's in the manuals). But, that's certainly not imaginative or getting appropriate ROI.
One also has to consider downtime. While downtime for an oil change on a CV isn't significant, it does add up. With the taxis, a 6,000 mile OCI corresponded to roughly one month. Change that to 3,000 miles, and it's every two weeks. I guarantee you that there are plenty of highway patrol vehicles that put on a lot more miles per day than do urban taxis. Looking at my 6,000 miles in one month, that gives an average speed of about 8.3 mph over 24 hours. There is plenty of idling between trips. City traffic is slow.
If a highway patrol car averages 30 mph, with two ten hour shifts, that works out to 18,000 miles per month (and that's a conservative estimate, based on what I've seen on some odometers from former highway patrol vehicles retiring to taxi service). If you change oil every 3,000 miles, that's 18,000 miles and 6 oil changes per month on one highway patrol vehicle alone.
The former highway patrol Impalas I've seen in recent years used the maintenance minder, and did a maximum of two or three oil changes per month on police service. For reference, I will see if I can get in touch with a friend that runs a very large taxi fleet now. He used to run LPG like I did, but now has moved to gasoline. I'll find out what his OCI is and see if he's had any longevity problems. He didn't do a lot of engine changes either; he used to personally inspect each vehicle each day, though I fear his fleet is now too large to allow for that. I'd ask my brother, who's still in the industry, but like I said previously, he's an idiot.
(Oil changes whenever, at the most expensive quick lube in town; filters that would make the Chinese counterfeiters blush)
As an aside, with respect to your comment that many taxis started life as something else, that's very true. If it's a Crown Vic or Impala, it was almost certainly a police car, and those tend to become available at roughly 100,000 miles (with fluctuation over some years due to budgetary concerns), since the police don't want to lose too much original value nor do they want to have a money pit on their hands with loads of downtime. If it's a Town Car, it's definitely been used, since new Town Cars were way, way too expensive to move directly from the dealer lot to taxi service.
In my years in the industry, I've seen a grand total of two brand new cars pressed into taxi service. One was ours, a 1986 Caprice bought brand new. That was a nightmare. First off, it must have been built on a Monday with all the little problems that popped up over the first few months. Aside from that, the loss on depreciation was never recovered. It was totalled off (like many taxis are) and insurers don't pay a lot of money for cars with hundreds of thousands of miles on the odometer. The engine ran beautifully and never consumed a drop of oil over the 6,000 mile OCIs. That didn't count for much on the back of a tow truck.
The other was a brand new minivan put into service by a colleague; he was the only driver on his car, plus one trusted part timer. He financed the thing back in the high interest days, and it simply didn't pay. He was an older fellow, and his only consolation was that he got to spend his days in a nice, new vehicle.
That's one major difference between police and taxi usage. The police must have a new, reliable, affordable vehicle and get their use out of it quickly, and move it out the door when they're finished with it, at a reasonable price, and if it's totalled off, well, them's the breaks. With a taxi, reliability and uptime are a concern, but you don't want to break the bank, knowing full well what insurance will pay on a high mileage vehicle, even if it's only three or four years old. A big hit like that is hard on a sole proprietor. At least in this jurisdiction, we can be paid a stipend by insurance for downtime due to a collision.
