I have just bought a Eunos Roadster and have filled up with Super Unleaded. My friend suggested using either supermarket E10 or Shell V-Power. What petrol is best for a mark 1, please? Thank you.
It will run happily on any petrol.
According to the gov site E10 is only confirmed ok for post 2005 MX5’s.
E10 contains enough ethanol to damage rubber seals/pipes on older specifications. Also it absorbs moisture so not good if the car is for occasional use or laid up over winter. Makes a right mess and can turn to a jelly like substance!
I’m stickingto E5, in other words super unleaded in the UK. Mainly due to doing so few miles and not wanting E10 sitting in the tank for prolonged time
There was a thread on this.
The NA Miata ran on gasohol, which is 10% ethanol pretty much from year zip. From the 1994 Miata owners handbook:
So 10% ethanol would not void the warranty. That’s a strong endorsement.
I asked questions of Mazda UK, and either they are idiots, or they simply don’t care about obsolete models (Mazda UK; if you are reading, please feel free to chime in, you have done rather will off the MX5 community over the years).
The responses indicated they really didn’t have a clue, and certainly were still spouting the same prejudice about imports as 20 years ago (they need to get over themselves).
Thank you for your email. I have checked with our Technical Support Team who have confirmed the information we have from Mazda Corporation states that for vehicles sold in Europe, only vehicles first produced (Not registered) after 2002 are compatible for use with E10 fuels.
I can confirm that vehicles sold in the US markets are subject to very different emissions laws and therefore differ in specification. Unfortunately, we do not have details of these differences as we only have access to the information relating to vehicles produced for sale in Europe.
And
We think the misunderstanding here is because the broader statement simply quotes the 2002 date, which relates to new model types introduced from this date – not individual vehicles registered from this date. For individual vehicle lines, the factory supplied us with the information shown on the DfT’s E10 compatibility tool which is also shown on the Mazda UK website.
To re-iterate, the information shown on the Mazda UK Website and within the Government’s E10 compatibility tool is correct for all vehicles that were originally built to UK specification. Unfortunately we are unable to confirm whether your understanding of the similarities between the Miata and the MX-5 are correct as we do not have this information. For non-UK models we would recommend that reference is made to the owner literature supplied with the vehicle to determine the correct fuel type.
In other words, Mazda UK, Mazda Japan, really cannot be bothered to:
I did a partial mapping using readily available online sources, but must have gotten bored of it. Mazda really ought to be doing this; if they really really think US cars had a fuel system that is significantly dfferent from other markets, and give the global supply of car parts now, they really have a Duty of Care to provide a rather better response than the half hearted response that raises the risk of NA cars catching fire. But really, they don’t care about NA owners, unless they are buying a new ND.
We all know the US is highly litiguous. The warranty statement is very strong. For them to have said that in 1994 indicates (1) they knew which parts were at risk (in contact with fuel) (2) they had carried out a materials analysis, which would have involved checking with suppliers. I am surprised Mazda UK is ignorant of this.
In the US, there are grades of fuel with very high ethanol content (E85); NAs might run a bit rough on this, but I have seen zero evidence of vehicle fires caused by ehtanol content in Miatas.
The revenue Mazda UK derives from NA parts sales must be by now insignificant, so I am not sure why they are evasive.
Some samples (EUDM; EU/EU spec. JDM; Japan spec, USDM; US spec. Used a 1996 vehicle as a reference) from my homemade comparison.
| Column 1 | Column 2 | Column 3 | Column 4 |
|---|---|---|---|
| **Market | Product Name | Part Number | |
| JDM | Filler pipe gasket | 0866-42-366B | |
| USDM | Filler Pipe Gasket | 0866-42-366B | |
| EUDM | GASKET,FILLER PIPE | 0866-42-366B | |
| JDM | Grommet | 8574-13-252 | |
| USDM | Fuel Injector Seal, Upper | 8574-13-252 | |
| EUDM | GROMMET | 8574-13-252 | |
| JDM | O-ring | 8574-13-253 | |
| USDM | Fuel Injector O-Ring | 8574-13-253 | |
| EUDM | RING,‘O’ | 8574-13-253 | |
| JDM | Evaporation hose | B61P-13-973A | |
| EUDM | HOSE,EVAPORATION | B61P-13-973A | |
| JDM | Drain hose | B61P-13-97YA | |
| JDM | Fuel pump filter | B61P-13-ZE1 | |
| USDM | Fuel Filter | B61P-13-ZE1 | |
| EUDM | FILTER,FUEL PUMP | B61P-13-ZE1 | |
| JDM | Fuel Distor Insulator | B675-13-158 | |
| USDM | Insulator Fuel | B675-13-158 | |
| EUDM | INSULATOR,FUEL DIST. | B675-13-158 | |
| JDM | Ventilation hose | B6CA-13-971 | |
| USDM | Hose Vent | B6CA-13-971 | |
| EUDM | HOSE,VENTILATION | B6CA-13-971 | |
| JDM | Evaporation hose | B6CA-13-972 | |
| USDM | Hose Evaporative | B6CA-13-972 | |
| EUDM | HOSE,EVAPORATION | B6CA-13-972 | |
| JDM | Fuel vapor valve | BC1M-42-980A | |
| USDM | Vapor valve | BC1M-42-980A | |
| EUDM | VALVE,FUEL VAPOR. | BC1M-42-980A | |
| JDM | Fuel injector | BP06-13-250 | |
| USDM | Remanufactured Fuel Injector | BP06-13-250 | |
| EUDM | INJECTOR,FUEL | BP06-13-250 | |
| JDM | Fuel distributor | BPE8-13-150 | |
| USDM | Fuel Rail | BPE8-13-150 | |
| EUDM | DISTRIBUTOR,FUEL | BPE8-13-150 | |
| JDM | Sub fuel pump | BPE8-13-350 | |
| USDM | Electric Fuel Pump | BPE8-13-350 | |
| EUDM | PUMP,FUEL-SUB | BPE8-13-350 | |
| JDM | Fuel pump | BPE8-13-35Z | |
| USDM | Fuel Pump Assembly | BPE8-13-35Z | |
| EUDM | PUMP,FUEL | BPE8-13-35Z | |
| JDM | Fuel hose | BPE8-13-495 | |
| USDM | Hose fuel | BPE8-13-495 | |
| EUDM | HOSE,FUEL | BPE8-13-495 | |
| JDM | Fuel hose | BPE8-13-49X | |
| USDM | Hose Fuel EGI | BPE8-13-49X | |
| EUDM | HOSE,FUEL | BPE8-13-49X | |
| JDM | O-ring | G601-13-253 | |
| USDM | Fuel Injection Pressure Regulator O-Ring | G601-13-253 | |
| EUDM | RING,‘O’ | G601-13-253 | |
| JDM | Check valve | GA5R-42-910 | |
| USDM | Check vlv | GA5R-42-910 | |
| EUDM | VALVE,CHECK | GA5R-42-910 | |
| JDM | Non-return valve | H260-42-270 | |
| USDM | Check Valve | H260-42-270 | |
| EUDM | VALVE,NON RETURN | H260-42-270 | |
| JDM | gasket | J004-60-962 | |
| USDM | Gasket | J004-60-962 | |
| EUDM | GASKET | J004-60-962 | |
| JDM | Injection insulator | JE06-13-257 | |
| USDM | Fuel Injector Seal | JE06-13-257 | |
| EUDM | INSULATOR,INJECTION | JE06-13-257 | |
| JDM | connector | JE16-13-298 | |
| USDM | Connector | JE16-13-298 | |
| EUDM | CONNECTOR | JE16-13-298 | |
| JDM | Canister | JE16-13-970A | |
| USDM | Vapor Canister | JE16-13-970A | |
| EUDM | CANISTER | JE16-13-970A | |
| JDM | Three-way valve | JE16-18-741 | |
| USDM | Valve | JE16-18-741 | |
| EUDM | VALVE,THREE WAY | JE16-18-741 | |
| JDM | Pressure regulator | KJ01-13-280 | |
| USDM | Fuel Pressure Regulator | KJ01-13-280 | |
| EUDM | PRESSURE RG.,FUEL | KJ01-13-280 | |
| JDM | In-tank fuel pump hose | KL19-13-ZE6 | |
| USDM | Hose Fuel Pump In Tank | KL19-13-ZE6 | |
| EUDM | HOSE,FUEL PUMP-IN TANK | KL19-13-ZE6 | |
| JDM | Filler hose | NA01-42-241C | |
| USDM | Filler Hose | NA01-42-241C | |
| EUDM | HOSE,FILLER | NA01-42-241C | |
| JDM | Fuel tank pad | NA01-42-762 | |
| USDM | Fuel Tank Pad | NA01-42-762 | |
| EUDM | PAD,FUEL TANK | NA01-42-762 | |
| JDM | Fuel tank gauge | NA75-60-960A | |
| USDM | Fuel Gauge Sending Unit | NA75-60-960A | |
| EUDM | GAUGE,FUEL TANK | NA75-60-960A |
And yet Honda say any of their cars with fuel injection is good to go. Toyota; anything from the 90s. Even Jaguar.
Pretty sure all the Japanese car makers use the same supply chain.
Damage to seals and pipes aside (and that debate will rumble on and on*), I have to say that my NB seems to like E5 better than E10. It may be confirmation bias, or whatever, but the extra octane in E5 seems to add a little extra oomph. That’s entirely unscientific, but there we are. And anyway, nothing’s too good for the Precious.
*Edited to add: ethanol has been added to gasoline in the USA for over 40 years with no furore there about NA fuel system damage (and they do love their class actions) so IMHO it’s a moot point.
That is my take on it also. Having looked into this when E10 came out, I decided also that nothing’s too good for my 93 Eunos. I only use V-Power and like the additional cleaning properties it brings.
E5 only in my 1993 Eunos
A capful now and again. Also, if you get “caught short” and have to fill up with E10, then add a measure before filling.
You will definitely know when you’ve added it.
I do fuel up on Tescos finest when I can but when I can’t I can’t say I notice a
difference. What’s so special about my 1.8 engine? It’s nothing special.
I fuel up on the ‘premium’ just to keep it as an option at the pumps.
i had a similar concern when i bought my mk1. i found that mx-5 restorer did a video on it on their lights up lights down youtube channel here:
bottom line is e5 or e10 are both fine, despite the fear mongering. if you have the spare cash to put premium in it, then why not? otherwise, so long as your car doesn’t sit untouched for months on end, super unleaded is fine.
Thank you to everyone for your considered replies. I will probably stick to super unleaded. I generally run my other car on super unleaded, but I don’t cover a lot of miles. I filled my other car with Tesco Momentum petrol yesterday and was returning 60mpg. I haven’t seen that figure for quite some time and never will in the Eunos.
Amongst E5s or supers as you said, the three hightest RON valued ones are Shell V Power, Tesco Momentum and Esso Synergy Supreme (ESSO’s E5). These three have RON 99.
ALL OTHER supers, or E5s, on any other UK forecourt (sainsbury’s, TEXACO, BP, Gulf etc) are RON97
(note TEXACO also do a RON 99, but very rare and not in many stations (https://texaco.co.uk/PublishingImages/Pages/Supreme99/Supreme%20Fuel%2099%20Performance+%20Stockist.pdf)
Also, amusingly, I emailed Texaco a while back (aug '23) and asked if they were going to extend their RON99 across more areas/stations. They emailed back saying ’ ‘we do not currently have any plans to release RON99 anywhere in the UK at the moment’… To which I emailed them their own website on RON99 and their own PDF of stations which sell it lol)
I have used E10 in my 1989 Eunos ever since it was available. Many thousands of miles on, it is absolutely fine with no sign of deterioration in any part of the fuel system, and it runs perfectly including on three track days. Ignition timing is set to the factory 10deg BTDC. I shall of course continue to monitor its pipework etc in case my confidence is suddenly misplaced…
John Simister (returning to the forum after about 14 years of absence)
