Improving the economy of an old BMW w/o buying fuel magnets & electric turbochargers

[genphreak]

FWIW: For anyone reading is wondering about ensuring optimum performance and economy in older Bimmers:

1. Avoid use E85 or E10 (or any ethanol fuel, it will destroy the fuel system gradually in an old car- they need to have been made with stainless lines, tanks and other fuelling parts to cope with it). Particulalry avoid using ethanol-laced fuel in a car that is left standing for any length of time (it will accelerate rust in the fuel tank).
2. Do not change fuels. Most BMW computers take 500km to get combustion right, changing fuel grade or even brand can destroy the balance it had acheived burning up the last tank.
3. If you have an auto trans, it's certainly worth keeping well serviced and rebuilt every 200k if you want a decent ride.
4. Other important aspects to cover are:
- make sure every vacuum hose, gasket and connection is air-tight and filters, sensors are refreshed- particuarly temp, O2 sensors, Fuel Pressure Regulator and AFMs
... all can be measured easily (first research and be careful testing O2 sensors and if in doubt, replace)
- watch for dirty injectors and poor spark due to plugs, coils and wires as well.
5. Keep the tyres at the right pressure and brakes in good order- little bits of drag wreck economy quickly.

[John B.]

I've had my 90 535i for 9 years & most of that time (7+ years) it has run on E10 fuel with no problems. I buy fuel where ever it is cheapest & have switched from Premium to 89 octane; again with no problems. On trips we get up to 27 mpg running 80 mph on the Interstate.

[ArnZ!]

I never run e10 in my 535i, every mechanic here says not to run it, in these older cars. It's only an extra 3 cents for normal unleaded.

[Russell]

Here in the US almost all fuel is e10. Of course you should avoid e85 as that stuff requires a car made to run 85% ethanol.

Sorry, I do not believe that switching brands has any measurable impact.

[Bill R.]

I've had my 90 535i for 9 years & most of that time (7+ years) it has run on E10 fuel with no problems. I buy fuel where ever it is cheapest & have switched from Premium to 89 octane; again with no problems. On trips we get up to 27 mpg running 80 mph on the Interstate.


I've got to agree with John, here in arizona in the larger cities e10 is mandated 6 months out of the year, the winter months. To reduce visible pollution. A number of stations sell it year round anyway. Its never had any harmful effects on my 89 535 and I get around 27 to 27.5 on the highway with the cruise on and a/c on. Factors i would look at for mileage are low rolling resistance tires, michelin makes a number of low rolling resistance tires that will increase mileage 5% or so. I would also check each brake caliper to make sure the boots are retracting the piston to reduce drag. I run mobil one 5w30 oil to run the lowest viscosity that i can get by with. I was running redline shockproof gear oil in my previa diff since they make some mileage and horsepower claims for it. Otherwise i would run the lowest multiviscosity gear oil thats allowed by bmw. I would run the stock width tires to reduce road friction as well. Engine tuneup etc etc

[genphreak]

Thanks for the comments gents, its an important topic these days!
... and the tip about thinner oil Bill, the last time I tried it the M30 valvetrain sounded pretty damn noisy so was leaving it off.

Many e34s have plastic tanks too so may be better about handling the corrosive effects. The link is between ethanol, corrosion and iron is certainly chemically, if not practically proven (in cars). However I've seen a number of 'issues' remarked upon in regards to seals and plastics that (don't?) like it either. I'll quote a recent defence dept document (http://www.defence.gov.au/im/policy/technical/ethanal_blended_unleaded_petrol/ethanol.pdf) (pdf) that was examining distribution infratrstucture (not cars, where heat and other stuff have different effects), but provides tons of practical advice:

"EtOH is a useful solvent for many substances and is used in the manufacture of many products including perfumes, paints, lacquer, explosives and Biofuel. It is miscible (mixable) in all proportions with water and with most organic solvents and is a flammable liquid with a flash point of 13o C and burns with a colourless flame. EtOH has a flashpoint higher than that
of Unleaded Petrol (ULP).

EtOH is most commonly used to increase octane ratings of, and improve the emission quality of petrol. It is recognised the emissions from EtOH blended fuels vary markedly between different EtOH/petrol blends and vehicle technologies, however within the Australian context, the use of ethanol blends of 10% ethanol/90% ULP (commonly known as E10) has been found to be greenhouse gas neutral. It should also be noted that E10 is the most common EtOH/petrol blend available worldwide; that the fuel is readily compatible with most modern automobiles and; with very little modification, E10 can be stored in existing distribution infrastructure.

At this stage the maximum content of EtOH allowed in Australian commercial ULP is 10% by volume (E10). However there are certain characteristics of EtOH that are different to
those of straight ULP, and thus the fuel requires particular management techniques in order for it to be fit-for-purpose and meet the regulated fuel standards.

PETROL/ETHANOL BLEND CHARACTERISTICS

Affinity to Water
Petrol has negligible solubility in water while EtOH in contrast, is highly water soluble. Petroleum fuels distributions systems are generally not designed to be completely water tight
but rather to tolerate small amounts of water. The ingress of water into a EtOH/petrol storage tank, results in the separation of water – alcohol phase from the petrol (phase-separation).
The amount of water ‘tolerated’ by an EtOH/petrol blend varies both with the EtOH content and temperature. Meaning the lower the blend content, the lower is the tolerance for water;
and the lower the temperature, the lower is the tolerance for water.

When phase-separation occurs in fuel tanks the result will be a reduced octane component in the petrol phase, and a separate water/EtOH phase with some hydrocarbons. As
noted, the petrol phase will have a lower octane content which may impact vehicle driveability depending on the petrol quality used to make the blend. Additionally, the
presence of a water/EtOH phase in the tank may foster microbial growth in tanks, and will encourage rust development. On the positive side EtOH will seek out any traces of water in a
storage system and hold the water in solution.
The paper goes on to reccommend:

Re-use of current Infrastructure for dispensing E10:
As noted above in paragraph 15, EtOH has a good solvent effect (or cleaning effect). It is also recommended that 10 micron type filters be installed between the fuel storage tank and
the final dispensing point to strain out any rust, scale, or dirt loosened from the tank walls or piping by the EtOH. These filters should be cleaned regularly. A good indication of blocked
filter is the slowing of product delivery flow at the nozzle. Is also recommended that water absorbing filters be installed to reduce the possibility of dispensing a water/EtOH blend if this
type of phase blend is present.

As for terminal pumps where E10 is used, pump seals should be either carbon or ceramic. If unsure, check with the pump supplier. The Australian Institute of Petroleum have been advised by the pump manufacturer Gilbarco Australia Limited that the pumps and dispensers it currently supplies to the Australian market have been designed to cope with
EtOH/petrol blend of no higher than 10 percent – E10. In addition, Gilbarco have provided the following warnings:-
a. higher levels of EtOH may damage elastomers in seals, diaphragms and other components;
b. aluminium, brass and zinc-plated components may be affected;
c. nozzles constructed of Elaflex ZVA may be damaged by EtOH content exceeding 10%;
d. Gilbarco also advised older Legacy pumps may not be able to handle EtOH/petrol blends at 10%.

If as the operator or maintainer you are unsure of the suitability of the equipment, it is recommended to check with the supplier of pumps and dispensers for information on
compatibility with EtOHl prior to the first delivery of EtOH/petrol blends, and the potential effect on warranties.
But wait, there's more...
Sealants
For Pipe sealants where EtOH/petrol blends are in use, avoid alcohol base sealants. Suitable sealants are; scotch brand pipe sealant with Teflon No 4178; Locite pipe sealant
Teflon No 592; and permatex seals pipes No 804, or similar industry approved products.
OK, nothing too scary, I guess- this is good news (untill Bill R checks out his injectors and shares the goodness)? :)