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BMW X3 vs Subaru Forester XT vs Infiniti FX 35 vs Toyota RAV4

1193 messages,  Last post on Apr 18, 2008 at 2:49 PM

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#1114 of 1193 Re: Wife's opinion X3 V Forester And my view backs seat [melbourne #1110] by edunnett Jun 28, 2004 (7:55 am)
Replying to: melbourne (Jun 27, 2004 6:11 pm) Melbourne - so you were told by a dealer to change the oil each 6000 miles instead of 3000? Or did you mean that the dealer told you to HALF and not double the interval between changes? -elissa Replies to this message: melbourne (Jun 28, 2004 2:08 pm)
#1115 of 1193 by p0926 Jun 28, 2004 (8:39 am)
Elissa- I'm pretty sure he meant double the frequency, not the interval. Of course most places that do oil changes (including dealerships) will recommend every 3k, if for no other reason than it doubles their business!   -Frank
#1116 of 1193 Re: Wife's opinion X3 V Forester And my view backs seat [edunnett #1114]Changing oil by melbourne Jun 28, 2004 (2:08 pm)
Replying to: edunnett (Jun 28, 2004 7:55 am) IMelbourne - so you were told by a dealer to change the oil each 6000 miles instead of 3000? Or did you mean that the dealer told you to HALF and not double the interval between changes? -elissa   Yes Elissa the "dealer" said to change the oil twice as often as recommended. However in fact, it was the salesperson, who is part time (we tested on the busiest day, as Saturday, so the person who road tested with us was a casual). He also was a hot up guru. He had bought about 10 WRXs and fixed them up and sold them. He now has a new job with one large bank, and he is aware that he hasn't actually made any money fixing up the WRXs: he said that the reality has been he's got some bad cars and then sold them after repair there now being excellant cars, and the owners have got the benefit.   He also said, (and this is a major negative on the XT for those BMW folk who see it as a criticism) he said that one should idle up the motor for a few minutes in the morning, and run it for a few minutes after any trip.   In Australia there were rumours that BMW would introduce turbo sixes. They know how to do it - in fact the 2002 turbo was the first production turbo car. Their turbo diesels are the best car diesel engines in their category. Mercedes supercharges their "chaff cutter" four cylinder engines. I feel if BMW did have a turbo six, they might have a strategy about keeping the bearing oil cool after turning off. But I don't know what they do with their current diesels.   I had a 99 SAAB turbo, the first true production turbo car, one of the first in Australia (mid 1970s). I remember on a night drive with friends, we stopped and I opened the bonnet: the whole of the engine bay was lit up by the glow of the still glowing red turbo charger.   Some vehicles have systems to pump the oil around the turbo bearings after turn off. I presume the Subaru has water cooling over the bearings. But I don't think there is an oil pump that circulates the oil that lubricates the bearings after one turns the engine off.   The Subaru uses an intercooller, which cools the intake air which increases its density and therefore its efficiency, espicially when ambiant temperatures are high. Such cool air would lower turbine temperatures. But the exhaust gas would be as hot as the SAABS, and that does heat up the turbine. I don't know what strategies Subaru uses to keep the turbine cool. Having a cool turbine is not really necessary anyway, except when the engine is turned off. Then the heat from the turbine will transfer to the turbines bearings, and the oil in the bearings will then absorb an awefull lot of heat. This heat breaks down the oil. So hence the turbo expert guy said change the oil twice as often, and run the engine before turbine use and after (in other words, warm the oil up before driving and after driving cool the bearings down by running the oil through the bearings by idling the motor).   I presume the reason why one runs the engine up before driving off is not just to warm up the oil though. If the engine has been switched off straight away, and the bearings have gotten hot from heat transfer from the turbine, the oil around the bearings can get very hot indeed. If this happens, the oil can break down. So if one runs the engine before driving, the turbine itself will not spin at idle. But the oil pump will push the oil around the bearings out. If the oil has broken down due to heat after switch off, any solids in the bearings will be pumped away. So idle it for a few minutes, and when you drive off and the turbo lightly spins, the good oil will be straight into the turbine bearings, and there will be no extra turbine bearing wear.   I would have no problem doing that, but I suspect my wife will not be bothered. I don't know how much it costs to replace the turbine bearings, and I don't know if a bearing failure would damage the turbine. I suspect the turbine would be designed maintain entegrity after a bearing failure. I's also imagine it would be designed to be cheap to replace the bearings. Nonetheless a bearing replacement is something that all turbos aventually have, but it is also something that can be avoided most particularly by idling the motor for a few minutes after use.
#1117 of 1193 by p0926 Jun 28, 2004 (2:19 pm)
Melbourne- The subject of whether special care (warm-up/cool-down) is needed for the FXT's turbo was discussed in length in another topic. A Subaru rep stated definitively that no such extra measures were required as the engine was designed to continue circulating oil after shutdown. I think this holds true for most manufacturer's current turbo models and the special care required by the 1980's era turbos are a thing of the past.   -Frank
#1118 of 1193 Oil and turbos by edunnett Jun 28, 2004 (3:55 pm)
Well, wether it's necessary or not (idling before and after take off) it sounds like it can't be a BAD idea? Or perhaps some good synthetic oil to avoid the heat breakdown that sounds like what we're trying to avoid in the first place? I'm going to switch to synthetic as soon as I run out of dino 5w30... (good lord, how many cases did I buy?!?!) - elissa
#1119 of 1193 by p0926 Jun 28, 2004 (4:48 pm)
sounds like it can't be a BAD idea?   Other than wasting gas and creating additional pollution? <Just kidding> No I'm sure it can't hurt, just like changing the oil more frequently than the manufacturer's recommend interval. If doing things like that make you feel better then by all means go ahead. After all, they're pretty cheap insurance for longer engine life.   -Frank
#1120 of 1193 by ateixeira Jun 29, 2004 (5:54 am)
I don't think there is an oil pump that circulates the oil that lubricates the bearings after one turns the engine off   Actually there is.   But it's still a good idea to be gentle until she's warm, true for any car.   In fact BMW pioneered a dynamic redline, where it starts out with a fuel cut off around 4000 rpm and gradually increases to the real redline after it's fully warmed up.   For cool down, generally you're idling right before you park. The last couple of blocks are in your neighborhood and you're likely going slowly. I wouldn't shut any car down after a hot lap. Cool down laps are, again, industry standard.   -juice Replies to this message: melbourne (Jun 29, 2004 1:47 pm)
#1121 of 1193 Re: [ateixeira #1120] Engine warm up techniques by melbourne Jun 29, 2004 (1:47 pm)
Replying to: ateixeira (Jun 29, 2004 5:54 am) Most Toyotas restrict engine revs on warm up, certainly the autos, which change gears early until the engine reaches operating temperatures.   However as to warm up, in Australia Toyota and BMW (our two vehicles) advise their owners to follow the hand book warm up instructions, which is to start and drive away, and drive gently until warm. This warms up everything, most especially the gearbox. Idling up to temperature does not evenly warm up the engine either. But in the case of the turbo, the WRX hot up guy must have seen quite a few knocked around engines I guess, and believes that idle warm up is very good for prolonging the turbo bearings. If Subaru could open the waste gate until the engine was warm, this might do the same thing. It would be kind of fun too ...   Good to hear that Subaru keeps pumping the oil after one cools off ... is the oil for the turbo bearings the same oil as the engine uses, or is it a separate loop?   Concerning engine life and oil changes, with our toyota SUV I rang Toyota who said ring Mobil (I was investigating using Mobil 1). Mobil said that Mobile 1 would be perfect in my SUV at 6000 miles, and that it would be just about perfect at 12000 miles. They said if I used Mobil 1, a top synthetic oil available for some years in Aus., that it would be stupid to use it and change it at only 6000 miles. But my engine was an less stressed Toyota V6, not a turbo ...   I think if my wife goes Forester XT, I'll ask her to be very gentle before and after! And to use Mobil 1 I guess. She has a 40 minute traffic drive to and from her work, which is ideal miles as the engine gets warm and is not turned off for 40 odd minutes. But I'll plead with her not to gun it down our street EVER, as she has done that with the BMW when its not warm and she's late ... I ahte to think about what stress an Forester engine would be taking especially if she had a more open exhaust ...
#1122 of 1193 by ateixeira Jun 30, 2004 (6:37 am)
Same, I believe.   Some say synthetic oil will outlive your oil filter. That's what limits the interval.   Long drives are best for your exhaust system, bet it never rusts.   -juice
#1123 of 1193 Engine cool down - what about the fan? by edunnett Jun 30, 2004 (8:30 am)
On my older Subarus I can recall hearing the fan running several minutes after shutting the engine off. Now I have the turbo and engine/turbo heat seems to be more of a concern, yet there's no fan running when I shut it off. Does anyone elses' XT run the fan after landing? elissa

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